I've never thought about this before...
I think there should be a way to replace the racial HD with class levels, just like it happens to every 1-HD race!
For example, a MM Satyr (5 HD) can be used as-is, and would be a sort of "Satyr commoner", a generic, class-less specimen of his race. But another Satyr could be a 5th level Rogue, and have 5 HD each one from a level of Rogue.
I don't mean to make this a gradual process, so that a Satyr could start class-less (5 racial HD) and then become a 1st level Rogue, replacing all benefits of his 5th racial HD with the first level of Rogue (or IOW having 4 racial HD + 1 Rogue HD). This may be too difficult, and it doesn't work well for PCs.
But at least there could be an option for games which start at a high level enough, to give up ALL the racial HD in exchange for the same amount of class levels. In a game which starts at level 7, a PC could be a Satyr with 5 class levels that would replace ALL benefits of the 5 racial HD (LA is still counted for its own purposes).
Would this be impossible?
edit: if you think about it, racial HD are always "weaker" than class levels... they grant the basic benefits of class HD (BAB, ST, HP, skills, feats) which could be better/worse depending on the class, but then they grant no other benefits (except increasing DC of special abilities) -> replacing racial HD entirely with class levels may actually simplify the calculation of CR