I agree with you that at 2nl you could play with the assumption everybody is an idiot until proven otherwise. However what you haven't perhaps thought of is the biggest mistake tendency at those stakes is calling bets and re-raises. 4betting mistakes tend to come from tilted players and maniacs. And if villain is an unknown he can be a:
1. a nit (doesn't make 4bet mistakes)
2. a tag (same as above)
and the two most likely opponent type:
4. a passive player (calls worse/better hands and 4bets premiums)
3. a maniac (4bets mostly worse but also better hands occasionally)
and then there is the fact that everybody gets better hands than AQ. Personally I would rather do a cheap mistake early when I have no info than an expensive one. And once I have classified the player type, I would start attacking his mistakes. As you go up in stakes and players make less mistakes, it is better to assume that re-raises mean strength and play tightly (even nitty). Because folding is rarely a mistake and when it is, it is cheap. And IMO you might as well make this assumption in 2nl so that you don't develop bad (=expensive) habits that will keep you from climbing the stakes.
Just my (nitty) thoughts on unknowns ♠_p: