Races in general aren't handled very well in 3e. The only PHB race that will make much of a difference past the first few levels is human. However, the difference is enough to make it so that many rogues are halflings, and few fighters are. They get a smaller die size weapon, but bonuses to Dexterity, Hide, and Move Silently. I don't see how you could change it without either overpowering halflings or changing the whole race system.