Yeah, but this is an exception.
It's not terribly unbalancing, since there's a BAB requirement and all that.
I did the same thing for the krogan.
EDIT: Well, maybe it could apply as a substitution for barbarian or whatever.
It's more of a racial level though, so maybe it shouldn't be called substitution?
As for the krogan, there's two different racial levels divided into 'classes' (kind of like PRC levels that need to be taken sporadically).
Holy crap, you found my old thread! Thanks.
Been googling around for that for ages.