The Crimson Binome
Hero
I think the fundamental weirdness is just a side-effect of odd stats being worthless in the game. A bonus of +3 to Con isn't actually worth more than +2 to Con, unless it's already at an odd number.Well it is a new way to think about feats, I get that. I actually take the fact that it's difficult to nail down the values as a good thing. Debate is an indication that the system has flexibility instead of shooting down the system as a whole.
Your system would make it easier to even out the random odd stat, and while that's definitely a boon to the players, I'm not sure whether it's an un-necessary buff, or whether the original system was un-reasonable to begin with. Was it supposed to be a balance measure, that increasing your Strength from 17 to 18 meant you also had to accept something less-valuable as the other half of the ASI? Or was it just an artifact of how ability scores work, that should be excised now that it's no longer necessary?
One benefit of the old system is that you can increase Strength directly from 18 to 20, in one swell foop. You never have to worry about accidentally raising it to 19, where it does nothing. I suppose your system would just have the character wait until they'd saved up enough points to go from 18 to 20 all at once, though.