In my next campaign, I've decided that even a 28 point buy is plenty, I want to kind of prove that high stats don't always make the PC (they just make things easier), and like the OP I want to start off a little low powered.
But since I like using dice for stat generation, I'm going to allow the players 3 options:
1) Roll 4d6 6 times, drop the lowest, in front of me, one total time. If you don't like the results
2) Standard point array +1. Meaning you get the six following scores placed however you want and then you can add 1 to any one of them: 8, 10, 12, 13, 14, 15
3) And if you don't like being limited to those specific number, then do a standard 25 point buy.
It's the best middle-ground I could come up with.