The elite_skeleton should work with the skeleton animation, but when i apply it and enter the game, i am unable to spawn the elite_skeleton. Also tried with the "giant", and with the "villager guards" mod, still was unable.

It is an entity with the same model and texture, but a different data structure than vanilla Minecraft.

https://www.youtube.com/watch?v=vEs1SXiLDVI&t=2s Try this method to make them Epic Fight style. I can't assure it works normally if they use different AI types.