And personnaly, the thing I would want them to change is the gameplay. Seriously, it's not good. Most of the time, I don't know what I am going to next, I just watch the move who is going to be done, when you focus on the arm for exemple with Alberto Del Rio, it's so boring, I would love it to be more fluid. Like I reversal and I can hurt the arm, I want this to looks like a real match. For the moment, the matches looks like video games matches and the reversal system is bad. No fluidity in the moves and it's too easy.
Having played every WWE game since Shut Your Mouth, I would say that WWE 13 is the most fluid WWE game ever made. The change in gameplay came in WWE 12, with the new "Predator Technology" system, which made the gameplay smoother and faster. Before WWE 12, especially in SvR 2011, the gameplay was very slow and didn't look like a wrestling match, however the incredible physics system saved SvR 2011.
There still needs to be some issues solved with the gameplay, but WWE 13 has the most realistic gameplay in the series.