Hey I've said stamina would have been nice to have in M&B: Warband, but I also said (in the same sentence or post) that it's way too late now to add it to Warband or C-rpg without breaking everything.
Forced first person and designing the game around it would have been nice as well, but way too late to do now.
Having in game voice comm would have been awesome as well (would need to make it proximity based). With the ease of being able to mute people from the scoreboard.