I wouldn't recommend Keepa, even as a later scorer. Players like Nedus can do the job just as well, and much better, in some respects.
One experiment I tried was having Brother as a centre. Because he was so incredibly fast, he took advantage of every other team (even the blasted Guado) and scored goal after goal. Needless to say, he was about 10 levels above everyone else, so the rest of my team suffered.
Was fun at the time, though. When he had the ball, he would charge forward, break their forward, shoot and score. When the enemy had the ball, he would take it from them first time, shoot and score. Ahhh, memories of 14-0 versus the Ronso.
Ahem. I can't suggest much in the way of other teams' players, since I distrust any player that isn't Al Bhed or insanely useful. But that's just me ;P