A system I've been trying to test involves not allowing races whose LA+RHD equals or exceeds the lowest ECL in the party, but otherwise ignoring LA (but not RHD.) That is to say, everyone in the party must be at least level 13 for a 6 RHD + 6LA race to be in play as a character race, but LA is not counted against the character for XP purposes, or for calculating total ECL.

LA only exists to encourage players not to play monster races, after all. If you prevent players from taking a powerful race at a low level, but allow them at higher levels when their power is less compared to PC classes, it's not as much of an issue. Being, for example, an Astra Deva is fun and long as everyone else in the party is level 21 or higher, it's not much of a power issue.