Having three different actions can make this difficult for left handers and even right hander's, Not everyone has guitar player like dexterity of the fingers or coordination especially when bullets are flying at you.

Adding a reactivating command too stand for the crouch and prone feature (or an additional option for it) would easily allow players to aviod using the stand button altogether and free up a key bind for other uses.

To be clear, you activate crouch, you activate the button again to retern to stand position. I think arma 3 works this way as well. Overall it would feel a bit more natural.