Suggestion: Have team chemistry, player chemistry (double play combinations, pitcher/catcher, etc), lineup chemistry, etc.
Reason: I think we're at the point now that, as GMs, we have to find the right players for our teams. FOF has had this forever...Wolverine's games all have this. If the player does not get along with teammates or coaches, the team will suffer. I think the ones listed will go the furthest towards adding another element to our universes. If we can grow that Tinker-to-Evers-To-Chance, or find someone who makes his pitchers better because of the way he handles the staff.
There is a great, great article on Pat Gillick on ESPN.com that describes the sort of thing I am talking about. You can read it
HERE.
Priority: I'd say high. I have never played anything SI...but if there is one thing I'd take out of that game and the games I listed, it is this. This above 2D, this above some online component...it's not a game-killer. But can you imagine how incredible this would be if we can embellish on the personalities of the players, and have to become cognizent of ALL players in our universe, so we can find the right fits for our teams? Hell, the Phillies were awful under Larry Bowa's fiery personality...and yet, the general core of this team has thrived under the more congenial, subtle Charlie Manuel.
There are an unbelievable amount of examples I can pull out. We should be able to make this a reality in our game, too.