I think a solution would be disabling 3d layers on parts of the skin which the essentials cosmetics will use as right now, 3d skin layers just overlaps the cosmetics

Player is also invisible in game, even with no cosmetics on

Looks fine to me? Don't have cosmetics to test, but yea if you add something to your skin and then a cosmetic at the same place, they will in fact clip into each other.

I believe this was caused by the FabricCapes mod, sorry about that