Encourage the optimizer to play something that is scaleable. That way when he needs to put the peddle down and save the party from a difficulty bungle or seven 1's in a row (I seriously rolled 4 in GDed row) he can. Don't be offended by me insinuating that you will bungle the difficulty at some point because it happens to every DM regardless of experience but even more so when you are newer. Sometimes you thought they would exploit the obvious weakness of a creature and then out of nowhere a party wipe happens. Having a player that can press a self realized oh **** button can be useful in those situations.

Down side of of this strategy is two fold. First, it can annoy the other players. When they are struggling fiercely, one player just seems to save their ass all the time tends to make them look weak or foolish. Nobody wants that kind of environment at their table, so use sparingly. Second, is sometimes the guy will handle the situation perfectly fine...and entirely alone. I had a character that was so strong compared to the rest of the party that the whole party wiped to 2 NPCs and I managed to defeat them by myself after the partys death. I couldn't save them from the DM's f'up (warforged Monk that was an optimized PC level character, and an optimized Wandificer of the same level. Two players died before initiative was rolled...), but didn't meet their fate, which was a really awkward situation, because I had just joined their game.

Still it's nice to have that guy that can use Celerity when it matters.