I'd personally like to see either the cost of an emag go up substantially, or for it to be reverted back to having limited uses. It's pretty unbalanced at its current cost, and seems to be the item every traitor buys instantly.
I'd like to see some sort of spirit medium, which can interact with ghosts through a lot of preparation. It'd probably take quite a lot of work to create and balance in a way that it's still fun to play, though.