I put this code into my Game.ini file:
NPCReplacements=((FromClassName="Basilisk_Character_BP_C",ToClassName="Basilisk_Character_BP_Shad_C"),(FromClassName="Crab_Character_BP_C",ToClassName="Crab_Character_BP_Shad_C"),(FromClassName="Raptor_Character_BP_C",ToClassName="Raptor_Character_BP_Shad_C"),(FromClassName="Carno_Character_BP_C",ToClassName="Carno_Character_BP_Shad_C"),(FromClassName="Rex_Character_BP_C",ToClassName="Rex_Character_BP_Shad_C"),(FromClassName="Megalodon_Character_BP_C",ToClassName="Megalodon_Character_BP_Shad_C"),(FromClassName="Gigant_Character_BP_C",ToClassName="Gigant_Character_BP_SCR_C"))
Will it work?

EDIT - 01/19/2025:
It did not work - the dinos still spawned as their vanilla variants and, as such, disappointed me. However, I used the mod Spawn Configuration. This mod actually fixes the random Alpha-Dino replacements, which interferes with the remapping of dinos that have an Alpha variant, causing the dinos to instead spawn as the vanilla variant (can very easily see this when the Rex still stops to roar, the Carno still sprints with its head down, the Megalodon still aggros you from the other side of the map, etc.). I put this code into my GameUserSettings.ini file to fix:

[SpawnConfiguration]
Remaps=Blueprint'/Game/PrimalEarth/Dinos/Giganotosaurus/Gigant_Character_BP.Gigant_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Giga/Gigant_Character_BP_SCR.Gigant_Character_BP_SCR',Blueprint'/Game/PrimalEarth/Dinos/Giganotosaurus/Gigant_Character_BP_TekCave.Gigant_Character_BP_TekCave':Blueprint'/Game/Mods/IceWyverns/InnerData/Giga/Gigant_Character_BP_SCR.Gigant_Character_BP_SCR',Blueprint'/Game/Genesis2/Dinos/BiomeVariants/Gigant_Character_BP_Rockwell.Gigant_Character_BP_Rockwell':Blueprint'/Game/Mods/IceWyverns/InnerData/Giga/Gigant_Character_BP_Rockwell_SCR.Gigant_Character_BP_Rockwell_SCR',Blueprint'/Game/PrimalEarth/Dinos/Rex/Rex_Character_BP.Rex_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Rex/Rex_Character_BP_Shad.Rex_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Carno/Carno_Character_BP.Carno_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Carno/Carno_Character_BP_Shad.Carno_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Megalodon/Megalodon_Character_BP.Megalodon_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Megalodon/Megalodon_Character_BP_Shad.Megalodon_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Raptor/Raptor_Character_BP.Raptor_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Raptor/Raptor_Character_BP_Shad.Raptor_Character_BP_Shad',Blueprint'/Game/Aberration/Dinos/Basilisk/Basilisk_Character_BP.Basilisk_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Basilisk/Basilisk_Character_BP_Shad.Basilisk_Character_BP_Shad,Blueprint'/Game/Aberration/Dinos/Crab/Crab_Character_BP.Crab_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Karkinos/Crab_Character_BP_Shad.Crab_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Rex/MegaRex_Character_BP.MegaRex_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Rex/MegaRex_Character_BP_Shad.MegaRex_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Carno/MegaCarno_Character_BP.MegaCarno_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Carno/MegaCarno_Character_BP_Shad.MegaCarno_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Megalodon/MEgaMegalodon_Character_BP.MEgaMegalodon_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Megalodon/MegaMegalodon_Character_BP_Shad.MegaMegalodon_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Raptor/MegaRaptor_Character_BP.MegaRaptor_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Raptor/MegaRaptor_Character_BP_Shad.MegaRaptor_Character_BP_Shad',Blueprint'/Game/Aberration/Dinos/Basilisk/MegaBasilisk_Character_BP.MegaBasilisk_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Basilisk/MegaBasilisk_Character_BP_Shad.MegaBasilisk_Character_BP_Shad,Blueprint'/Game/Aberration/Dinos/Crab/MegaCrab_Character_BP.MegaCrab_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Karkinos/MegaCrab_Character_BP_Shad.MegaCrab_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Rex/BionicRex_Character_BP.BionicRex_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Rex/BionicRex_Character_BP_Shad.BionicRex_Character_BP_Shad',Blueprint'/Game/PrimalEarth/Dinos/Raptor/BionicRaptor_Character_BP.BionicRaptor_Character_BP':Blueprint'/Game/Mods/IceWyverns/InnerData/Raptor/BionicRaptor_Character_BP_Shad.BionicRaptor_Character_BP_Shad'

(Note that there may be a typo or 2 in this, don't scream at me if the wild Carnos still have to run at you with their head down as if they are trying to be a Woolly Rhinoceros)