Things that I would really want them to focus on:
1. Gameplay. Want the standup and ground game to feel very real and not robust.
2. Training. In career mode there should be minigames you have to compete in to upgrade your MMA discliplines (Muay Thai, BJJ, Wrestling etc.)
3. Career Mode. A nice in depth mode where ya can take a fighter from amateur thru a 20 yr career (start at 20 finish at 40 etc.)