I'm tending to agree with Jefe. I guess it's stated in the OP that the purpose is to find a use for attribute proper (as opposed to attribute mod), so it isn't just how it feels, it's a stated goal.
I think you are right, we can make simple changes and put them on a sheet. However, at the end of the day I think we'll be making a lot of simple changes to address the consequences of the change. And, other than the purely aesthetic value of finding a use for a game number, I don't see what it accomplishes. The part of the OP about 'no longer have to calculate DCs on the fly or just make up random numbers for DCs' is true, but not specific to this implementation (the same could be accomplished with the 8+prof+ability mod model as well).
I think it's an interesting idea for a theoretical alternate D&D-like game. But for the existing game, it seems like a lot of little modifications without a specific payoff.