Maybe. But I think the reason that they are NOT used is that it is harder to understand what the difference is (story-wise) between, say, a WIS save, and a CHA save. (And I can only guess why they made things like Illusions into INT (Investigation) checks instead of INT saves)Is the issue that there are six saves or is it that only half are used? If all six were used roughly equally would that be okay?
The three physical abilities' saves are all used, because it's easy to see what they're for (even if STR saves are often interchangeable with STR (athletics) checks).
Of course, they could ALL be ditched for skill checks, with a better skill system, if they wanted to go that way.