Ah, I see. There is a certain symmetry in having the apex of natural potential match the absolute maximum advantage for training. Personally, I think that someone who began completely average but has completely mastered a "skill" (whether we're talking about combat, lockpicking, or brickmasonry) should be better than someone with no training but great potential. Of course there are other (and arguably better) ways of modeling skill than just a bigger bonus. Special abilities that allow you to do things an untrained person can't, for one.
As far as the magic bonuses, I actually agree with you. I was disappointed the moment I saw a +1 sword. Then I said, "Hey, the +1 sword is iconic in it's own way. I can live with that" Aaaand then I saw they scaled up to +3. Myself, I would prefer that the average "magic blade" offered no bonuses to attack. Just cool special abilities. Then there would be the VERY rare high power magic items that grant a +2 along with their other stuff. When a player got that it would matter, because nothing ever ups your hit. So that sword would feel that much more special.
The biggest problem I see with your idea (just my opinion, of course) is that there's not enough room to customize between characters. Having ability scores add a generic bonus to all checks that have to do with them is simple and a good way to go. (As opposed to loads and loads of charts or multiple different rulesets for different kinds of strength checks). But only allowing the pinnacle of human ability to be 5% more likely to pull off kicking down a door than Joe Wizard makes ability scores not matter enough.