[SpAwNtHeKiLlEr]

Tyrael wouldn't fit in for many reasons.
1) He is not played in any games.
2) The only game he is in is Diablo II but he is a npc. The only time he shows up is in act 2 when you defeat duriel and act 4 when you defeat diablo and are going to harrogath and when you defeat baal.
3) Although he would be a kick ass character to play, he doesn't walk he floats above the ground. It would be easy to incorporate walking but also you need to make him look perfect on the game and he needs to have a weapon and everything planned out.
4) He would need to be adjusted into a 3d version unless if you just take him straight from the video in diablo II.