Perhaps a limitation on jumping, as online gameplay consists of very unrealistic hopping about. I think the game could be just as fun if not moreso with that limited somehow, either with a loss of accuracy during a jump or no airborne firing ability whatsoever.
Seems like it would make accuracy a more valuable asset instead of the "spray and pray" method. Or maybe if this was a server level option, so some servers could indulge in the mad hopping about style, and others could take a more realistic approach?
