first off, wow you got it running on a server? did you have to give it like 128GB of ram?
anyway there is a way to kinda make custom player stomachs but its annoying and involves messing with nbt stuff. at the moment there is no way to make player stomachs. this is pretty much due to limitations wit the mod maker thingy. but also my passion for minecraft is gone.
also yeah multiple players should be able to be eaten by the same player.