So basically I don't like that 4d6 drop the lowest often gives a large spread between the best and worst PC stat-wise (and, as a result, character power level).
I don't like that point buy results in cookie cutter PC's. Requiring 3 odd and 3 even stats still won't change the fact that almost all fighters will have high Str and Con and low Cha and Int, all Clerics will have high Wis and lower Dex, etc.
Hmm. I think that's kind of contradictory, but we'll see. How about this:
The player chooses a class, and then chooses 1 primary ability and 1 secondary ability.
For the primary ability, she rolls 14 + 1d4.
For the secondary ability, she rolls 12 + 1d6.
For the other four abilities, she rolls 4d6, drop the lowest, in order. That is, Str, Dex, Con, Int, Wis, Chr, skipping over her primary and secondary ability.
So if she wanted a fighter, she would roll 14+1d4 for Strength, giving a Str score between 15 and 18. Then 12 + 1d6 for Con giving a Con score from 13 to 18. Then 4d6 drop lowest for Dex, Int, Wis, Chr in order, giving a completely random set of numbers.
This guarantees solid, decent scores for the two most important abilities for the class. However, the rest of the character is organically rolled. There are no "dump stats". You might end up with a smart fighter, or a wise fighter, or a charismatic fighter, but you can't predict it.