The Binding of Isaac: Rebirth

The Binding of Isaac: Rebirth

Mei
True co-op support?
So the people that made true coop wrote that the tools to make mod characters selectable for the other players is there for the characters creator, but there doesn't seem to be any mod characters that do this. Basically all mod characters don't work with true co-op and I'm trying to raise awareness.
Is it difficult to do? Has no one thought about it? Is it possible to make this work by updating the character mod, or by making a secondary mod, or can a mod menu be made for this?