I've been bouncing back and forth on this for several years. Yes, that works fine for a Lizardman, whose CR is only double that of a normal person. But what about Thrym, King of the Frost Giants? Even a maxed out Leadership score gives him like 2 commoners as followers! Less if you use the LA adjustor and their HD.
Giving them commoners/warriors/experts of their species is equally fraught with danger since Thrym would have 135 "common" frost giants, 13 with 1 NPC level, 7 with 2 NPC levels, 4 with 3 NPC levels, and 2 each who have 4 and 5 NPC levels.
I lean towards the latter simply because it is more realistic but am hesitant to see how PCs might abuse it.