Well, the reason I'm trying to remove stat-enhancing items is two-fold. First of all, the campaign as a whole is low-magic, though the PCs are much closer to standard magic. So in general, I'd like to maintain standard PC power levels, while reducing the number of magic items in the game at the same time. The second reason is that, in general, I think stat-enhancing items, though powerful, are also fairly boring. I'd rather hand out ancient swords and dragon shields, than another belt of giant strength.
Thanks for all the ideas so far. A few more thoughts:
1. I'm considering tying the bonuses to a magic item. Each character would have one, and this item's main power would be "augmenting human potential." It would help to explain why the PCs wind up being so much stronger, smarter, and faster than the average commoner. But it would be only one item no matter how the PC divvied up the stat bonuses, and the bonuses would be inherent and not lost if the item is lost (though no further bonuses would accrue.)
2. I'm beginning to see that there's a gray area in regards to who gains stat boosting items when. The consensus seems to be 4-5/8-10/12-15. I'd rather err on the side of conservatism, so I'm considering +1 bonus every other level, with a maximum bonus for any one stat of 1/2 level -1. So the progression would look like this:
Level...Max Bonus
1 ... +1
2 ... +1
3 ... +1
4 ... +1
5 ... +1
6 ... +2
7 ... +2
8 ... +3
9 ... +3
10 ... +4
11 ... +4
12 ... +5
13 ... +5
14 ... +6
15 ... +6
16 ... +7
17 ... +7
18 ... +8
19 ... +8
20 ... +9
On top of this, I may award an additional point or two in-game after certain events. (Natural 20 on caster-level check for wizard, crit confirmed by another natural 20 for fighter, etc.) These bonuses would also be explained by the single item the PCs had been given.
Thoughts? Suggestions?