Aren't CR's for NPC-Class equal to Level-1 ?!?
I don't know the excat rules because I don't have my DMG at hand, but to be fair to the players I would have to ask myself:
If I can exchange the Warriorclasslevel with every other class without changing the CR, whats more Challenging: A fey-ri with a level of warrior, one with a level of comoner or one with a level of babarian?
If you replace te Warrior with level of Babarian it is IMHO clear that this is somehow unfair to the players (Same BAB, same Saves, same Weaponprofiences, but: better HP, Rage, fast movement, more Skills). This is even more unfair if I compare the babrian to zhe comoner.