A quick model breakdown:
2x Lord Celestant on Dracoth
4x Lord Relictor
4x Prosecutor Prime
8x Prosecutor
= 12
4x Retributor A
4x Retributor B
4x Retributor C
= 12
4x Liberator Prime A
4x Liberator Prime B
8x Liberator A
8x Liberator B
8x Liberator C
8x Liberator D
= 40
Stormcast have 3 different Hero models, Paladin armour, Liberator armour and with Wings (Paladin Armour with Wings for the Celestant Prime)
There are 6 different Liberator models, 3 different Retributor models (4 with the Relictor) and 2 different Prosecutor models.
This are enough different models to convert each Hero from a different model and be able to use different models as base for the same Hero if I need them twice.
Liberators:
Lord Castellant - Prime B/Liberator A
Knight-Heraldor - Prime A/Liberator C
Knight Incantor - Liberator B/Liberator D
(Knight Questor - Liberator A)
(Knight Veritant - Liberator B)
(Lord Arcanum - Prime B)
2x5 Liberator
2x5 Judicator (flaming Bows or Javelins, not using the Prime models here)
= 8 Liberator and 3 Liberator Prime left
Paladins:
Lord Relictor - Relictor/Relictor
Knight Vexillor - Lord Relictor/Retributor C
Lord Celestant (food) - Retributor A/Relictor
2x5/1x10 Retributor/Protectors
= 0 models left
Prosecutors:
Knight Azyros - Prosecutor A
Knight Venator - Prosecutor A/Prosecutor B
2x3 Prosecutors with Javelins
= 0 models left
Dracoth Rider:
Lord Celestant on Dracoth - Celestant on Dracoth
or
1x2 Fulminators - Celestant on Dracoth
= 1 or 0 models left
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11-14 Liberator models left (Questor, Arcanum and Veritant are optional) with enough Heroes and 4 Battleline units to modify the list and the possibility to field 10 Liberators. Other Heroes are named/unique or so I am not sure if it makes much to convert them neither have I models to make the mounted ones (though I have an old Chaos Knight/Pegasus Conversion that would fit a Lord-Arcanum on Tauralon)
Possible uses for those:
3-9 Vangaurd Raptors with Longstrike Crossbow (not sure how to convert those without the Bits)
5-10 Evocators (could be tricky to get the robes right)
3 Raptors + 5 Evocators would leave 3-6 Liberators for bits and/or later use
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possible non-Stormcast models:
Mantics KoW Naids would make a nice substitute for Skinks if allies are needed
Old Warhammer
Empire Barded Horses or
Goblin Wolves with Eagle/Falcon Heads would make decent Gryph Hounds (will surley make a test model)
Puppets War Raven can be used as Aetherwings, but with 28mm wingspan they are to small for a real replacement
Raging Heroes Ascended Sister Erzebel, Great Seraphim would be a nice Celestant Prime, and I have one laying around anyway
Converted Khorne Pegasus re-converted into a Lord-Arcanum on Tauralon (too small but just because I can)