The one word answer to the OP question: SOMETHING.
Kofi's going to stay in neutral forever as long as the bookers keep ignoring him. He'll never ever ever get over without some kind of storyline direction, no matter how good he is in the ring. As was already mentioned, he's just fine in the role he's in, bouncy midcarder who puts on a decent show for the fans on TV. But I'd hate to leave this stone unturned. Give him a heel turn and a gimmick. Give the fans a reason to react to him. I can't help but think he can improve on the microphone with some direction. If it doesn't work out, hell, you can always put him back where he is now. But he's been around for a while, he's one of the few entrenched midcarders they have, and the fans like him. Why not see if it's possible to take it further?