If you don't have nationals, just use the fallback output.
The chances to pull from the "national pool" varies depending on the creation method:

• Effect 37 rituals, (remote summons, like Army of the Dead)
  • 50% chance of national longdead for Commander
  • 10% chance of national longdead for Troops

• Effect 1 rituals, (summons, like Reanimation)
  • 100% chance of national longdead

• Priest Reanimation order, chance depends on your nation:
  • MA Ermor, Sceleria:
    • 10% chance of national longdead
  • Niefelheim, Jotunheim, Utgard:
    • 25% chance of national longdead
  • Hinnom, Ashdod:
    • 50% chance of national longdead
  • Any other nation:
    • 75% chance of national longdead

• Otherwise, there is a 10% chance to get nationals.

• Equal chance to: pick one of these 6; Longdead, Longdead, Longdead, Longdead, Longdead, Longdead

• 50% to use fallback,
• Otherwise:
  • 50% chance for: Longdead Giant
  • Else: Longdead Giant

• 50% chance to use fallback,
• Otherwise:
  • 100% chance for: Longdead Giant

• 50% chance to: pick Longdead Velite or Longdead Legionnaire,
• Else: pick Longdead Triarius or Longdead Principe

• Equal chances to: pick one of these 3 Longdead, Longdead, Longdead Hoplite

• Equal chances to: pick Longdead or Longdead

• 75% chance for: Longdead,
• Otherwise: use fallback

• 85% chance to: pick Longdead or Longdead,
• Otherwise: use Longdead

• 25% chance to: use Longdead,
• Otherwise: use fallback.

• Equal chances to pick one of these 5; Longdead of C'tis, Longdead of C'tis, Longdead of C'tis, Longdead Warrior, Longdead Warrior

• Equal chances to pick one of these 4: Caelian Longdead, Caelian Longdead, Caelian Longdead, Caelian Longdead

• Equal chances to: pick Nazcan Longdead or Nazcan Longdead

• 50% chance to: pick one of these 3; Longdead Rephaite, Longdead Rephaite, Longdead Rephaite,
• Otherwise: use fallback

• 2/7 chance to: pick one of these 3; Longdead Bandar, Longdead Bandar Warrior, Longdead Bandar Warrior,
• 1/7 chance to: pick one of these 3; Longdead Vanara, Longdead Vanara Warrior, Longdead Vanara Warrior,
• Otherwise: use Longdead Markata

• 15% chance to: use Longdead,
• Otherwise: pretend you are Berytos

• 50% chance to: pick Longdead or Longdead,
• Otherwise: use Longdead

The result of each soulless request depends on a few things:

• The nation creating soulless
• The province ID the soulless are being made in
• A chance for national soulless
• A chance for arming soulless
• The number of corpses to subtract

Sources and values for national and arming rates for the above:

• Montag -3:
  • 10% national, 100% ArmingChance

• Montag -15:
  • 25% national, 50% ArmingChance

• "newunit" called with unit ID -1, unknown if this is used:
  • 10% national, 100% ArmingChance

• Battlesummon, damage -3:
  • 10% national, 100% ArmingChance

• Reanimator priests:
  • 90% ArmingChance, but national rate varies:
    • If Jotunheim, 50% national
    • If Utgard, 25% national
    • Any other nation:
      • Reanimator priest holy level is considered as 1 higher if ((closed d5 - 1) < number of friendly candles) in province,
      • National soulless rate = (reanimator priest's holy level * 8)%

• Rituals, effect number 1 [summons, though there are no base game rituals that summon Soulless this way]:
  • 100% national, 90% ArmingChance

• Rituals, effect number 37 [remote summons, like Carrion Reanimation]:
  • Units:
    • 10% national, 10% ArmingChance
  • Commander:
    • 50% national, 90% ArmingChance

• If there is a province ID associated with this creation:
  • Roll soulless ArmingChance, if successful proceed as making Lightly Armed soulless
  • Otherwise, if (Civilian corpses < Military corpses):
    • Proceed as making Lightly Armed soulless
• Armed Soulless upgrade chances:
  • In EA,
    • 25% chance to: upgrade Lightly Armed to Medium Armed soulless
  • In MA,
    • 50% chance to: upgrade Lightly Armed to Medium Armed, and if that succeeds:
      • 25% chance: to upgrade to Heavy armed soulless (total of a 1/8 chance)
  • In LA,
    • 75% chance to upgrade Lightly Armed to Medium Armed, and if that succeeds:
      • 50% chance: to upgrade to Heavy Armed soulless (total of a 3/8 chance)
• If there wasn't a province ID, you always get Unarmed soulless

• If this attempt is subtracting corpses, do that now.
  • Unarmed soulless subtract Civilian corpses
  • Any kind of Armed soulless subtract Military corpses

• Unarmed:
  • Soulless
• Light:
  • Soulless Warrior
• Medium:
  • Soulless Warrior
• Heavy:
  • Soulless Warrior

• Jotunheim, Niefelheim, Utgard:
  • Unarmed:
    • 50% chance to become: Soulless Giant
  • Light, Medium:
    • 50% chance to become: Soulless Warrior
  • Heavy:
    • 50% chance to become: Soulless Warrior

• EA, MA, LA Caelum:
  • Unarmed:
    • Becomes: Soulless
  • Light:
    • Becomes: Soulless Warrior
  • Medium, Heavy:
    • Becomes: Soulless Warrior

• EA Ur, MA Uruk:
  • Unarmed:
    • 75% chance to become: Soulless Enkidu
  • Light:
    • 75% chance to become: Soulless Warrior
  • Medium, Heavy:
    • Becomes: Soulless Warrior

• Nazca:
  • Unarmed:
    • Becomes: Soulless Nazcan#2707
  • Light, Medium, Heavy:
    • Becomes: any one of these 4; Soulless Nazcan Warrior, Soulless Nazcan Warrior, Soulless Nazcan Warrior, Soulless Nazcan Warrior

• EA, MA, LA Atlantis:
  • 75% chance to:
    • Unarmed:
      • Becomes: Soulless of Atlantis
    • Light:
      • Becomes: Soulless Warrior
    • Medium, Heavy:
      • Becomes: Soulless Warrior
  • Otherwise:
    • Unarmed:
      • Becomes: Soulless Shambler
    • Light:
      • Becomes: Soulless War Shambler
    • Medium, Heavy:
      • Becomes: either Soulless War Shambler or Soulless War Shambler

• EA, MA, LA R'lyeh:
  • 75% chance to:
    • Unarmed:
      • Becomes: Soulless of Atlantis
    • Light:
      • Becomes: Soulless Warrior
    • Medium, Heavy:
      • Becomes: Soulless Warrior
  • Otherwise:
    • Unarmed:
      • Becomes: Soulless Shambler
    • Light:
      • Becomes: Soulless War Shambler
    • Medium, Heavy:
      • Becomes: Soulless War Shambler

• EA, MA, LA C'tis:
  • Unarmed:
    • Becomes: Soulless of C'tis
  • Light:
    • Becomes: Soulless Warrior
  • Medium, Heavy:
    • Becomes: Soulless Warrior

• Kailasa, Lanka, Bandar Log, Patala:
  • Roll a closed d7, then,
  • If unarmed soulless, and:
    • d7 result is 1-2:
      • Becomes: Soulless Bandar
    • d7 result is 3-5:
      • Becomes: Soulless Vanara
    • d7 result is 6-7:
      • Becomes: Soulless Markata
  • If d7 result was 1-2, and:
    • Light:
      • Becomes: Soulless Bandar Warrior
    • Medium:
      • Becomes: Soulless Bandar Warrior
    • Heavy:
      • Becomes: Soulless Bandar Warrior
  • If d7 result 3-4, and:
    • Light, Medium, Heavy:
      • Becomes: Soulless Markata
  • If d7 result 5-7, and:
    • Light:
      • Becomes: Soulless Vanara Warrior
    • Medium, Heavy:
      • Becomes: Soulless Vanara Warrior

Each soulless request depends on a few things:

• The nation creating soulless
• The province ID the soulless are being made in
• Chance for national soulless
• Chance for armed soulless
• The number of corpses to subtract

Sources and values for the above:

• Montag -3: 10% national, 100% armed
• Montag -15: 25% national, 50% armed
• "newunit" called with unit ID -1: 10% national, 100% armed, unknown if this is used
• Battlesummon, damage -3: 10% national, 100% armed
• Reanimator priests: 90% armed, national rate varies:
  • If Jotunheim, 50% national
  • If Utgard, 25% national
  • Any other nation:
    • Reanimator priest holy level is increased by 1 if (closed d5 - 1) < number of friendly candles in province
    • National soulless rate = (reanimator priest's holy level * 8)% national
• Rituals, effect number 10001 [regular summon units in local province, like Reanimation]: 100% national, 90% armed
• Rituals, effect number 10037 [remote summon permanent units]:
  • Units: 10% armed, 10% national
  • Commander: 50% national, 90% armed

Process:

• If there is a province ID associated with this creation:
  • Roll armed soulless chance, if successful proceed as making lightly armed soulless
  • Otherwise, if civilian corpses < armed corpses:
    • Proceed as if making lightly armed soulless.
    • In EA, there's a 25% chance to upgrade to medium armed soulless
    • In MA, there's a 50% chance to upgrade to medium armed, and if that succeeds there's a 25% chance (so a total 1/8) for heavily armed soulless
    • In LA, there's a 75% chance to upgrade to medium, and if that succeeds there's a 50% chance (so a total 3/8) for heavily armed soulless
• If there wasn't a province ID, you always get unarmed soulless.
• If this attempt is subtracting corpses, do that now. Unarmed soulless subtract civilian corpses, any kind of armed subtract military corpses.
• Default soulless types:
  • Unarmed: Soulless#197
  • Light: Soulless Warrior#914
  • Medium: Soulless Warrior#915
  • Heavy: Soulless Warrior#2119
• National soulless:
  • Jotunheim, Niefelheim, Utgard:
    • Unarmed: 50% chance to be changed to Soulless Giant#315
    • Light, Medium: 50% chance to be changed to Soulless Warrior#916
    • Heavy: 50% chance to be changed to Soulless Warrior#917
  • EA, MA, LA Caelum:
    • Unarmed: Changed to Soulless#317
    • Light: Changed to Soulless Warrior#2242
    • Medium, Heavy: Changed to Soulless Warrior#2243
  • EA Ur, MA Uruk:
    • Unarmed: 75% chance to be changed to Soulless Enkidu#2981
    • Light: 75% chance to be changed to Soulless Warrior#2982
    • Medium, Heavy: Changed to Soulless Warrior#2983
  • Nazca:
    • Unarmed: Changed to Soulless Nazcan#2707
    • Light, Medium, Heavy: Changed to any Soulless Nazcan Warrior#2708-27011 at equal weighting
  • EA, MA, LA Atlantis:
    • 75% to…
      • Unarmed: Changed to Soulless of Atlantis#318
      • Light: Changed to Soulless Warrior#919
      • Medium, Heavy: Changed to Soulless Warrior#920
    • Otherwise…
      • Unarmed: Soulless Shambler#2364
      • Light: Soulless War Shambler#2365
      • Medium, Heavy: Either Soulless War Shambler#2366-2367 at equal odds
  • EA, MA, LA R'lyeh:
    • 75% to…
      • Unarmed: Changed to Soulless of Atlantis#318
      • Light: Changed to Soulless Warrior#919
      • Medium, Heavy: Changed to Soulless Warrior#920
    • Otherwise…
      • Unarmed: Soulless Shambler#2364
      • Light: Soulless War Shambler#2365
      • Medium, Heavy: Soulless War Shambler#2366
  • EA, MA, LA C'tis:
    • Unarmed: Changed to Soulless of C'tis#319
    • Light: Changed to Soulless Warrior#921
    • Medium, Heavy: Changed to Soulless Warrior#922
  • Kailasa, Lanka, Bandar Log, Patala:
    • Roll a closed d7.
    • If unarmed soulless:
      • d7 result is 1-2: changed to Soulless Bandar#1716
      • d7 result is 3-5: changed to Soulless Vanara#1724
      • d7 result is 6-7: changed to Soulless Markata#1731
    • If d7 result was 1-2:
      • Light: Soulless Bandar Warrior#1717
      • Medium: Soulless Bandar Warrior#1718
      • Heavy: Soulless Bandar Warrior#2274
    • If d7 result 3-4:
      • Light, Medium, Heavy: changed to Soulless Markata#1731
    • If d7 result 5-7:
      • Light: Changed to Soulless Vanara Warrior#1725
      • Medium, Heavy: Changed To Soulless Vanara Warrior#1726