Status and power levels are good ideas. Maybe characters could use points to purchase new powers that wouldn't necessarily have sex applicability, or that could expand their canon capabilities, or begin to power up unpowered characters. Maybe they could also use points to purchase items that could influence other characters in a sexy way (obviously they wouldn't be able to godmode another player just because they had magical item x, but it could be a plot point that led into more kink - like, say, a collar that once put on character y, rendered character y subservient to character x for an arbitrary period of time)