Fundamentally, ability scores are too important to the game, to the extent that I see a lot of discussions of building characters where the choice of race is determined not by "I want to play a Shardmind", but rather because the player wants to optimise his character by getting that juicy +2 bonus to just the right stat.
Anything that increases stats after character creation actually serves to aggravate the problem - suddenly you have to throw every bonus at that prime requisite just to stay competitive, and a less experienced player (who doesn't know to do this, or who doesn't buy the right items) inevitably falls behind. (Plus, if the game effectively requires you to keep boosting that one stat, then what is the point of having the stats in the first place? It's a 'choice'... but it's a choice to suck or not to suck.)
And, of course, in 3e it was much worse than in 4e - because stats were foundational to everything else, any change to the stat meant a cascade of changes to lots of elements on the character sheet. 4e did well to remove temporary stat mods; 5e should take the next step and get rid of the permanent ones, too.
So, I'm very much of the opinion that stat modifiers in general should be lower, and pretty much everything that changes a character's stats should likewise be eliminated. (With a probable exception for the most powerful magics - the equivalent of the old unlimited wish.)
All IMO, of course.
That's an interesting approach, and would certainly be workable. It would be a pretty major change, though.
Besides, I still think I prefer the model where your stats represent your innate potential, while your levels/feats/skills represent the training you have received. Under which model, when Bruce Wayne trains to become Batman, he doesn't increase his stats - he gains lots of levels and skills that allow him to maximise his innate potential.
