Let's say with this new FP+ system you are able to choose your 3-4 fastpasses for the day ahead of time. And if you qualified for a GAC with the old system, you are now qualified for an additional 3-4 fastpasses for the day, and they can even be repeated fastpasses - i.e., your initial 3-4 FPs must all be for different attractions, but your additional ones may repeat each attraction one additional time, if you would like to. (Obviously, this is all hypothetical. I have no idea if this is how it's going to work out).
Now you can plan your day appropriate to your needs. Obviously, you won't be able to go from ride to ride with an instant FP like you do now, but in between FPs you will have enough time for those longer bathroom visits, you will still be able to walk at your slower pace if needed from attraction to attraction, you can see an air conditioned show in between FP (which so rarely have a wait beyond waiting for the actual show time itself) or at least take a breather in the shade, and you can even plan for an extended break between FPs so that if you're one of those who need to leave the park for a rest you are able to.
Obviously there is still a benefit as you would get twice as many fastpasses as non-disabled guests, however, it would still significantly cut down on the abuse seen now (i.e. guests who use their GACs to access an e-ticket's FP line 15 times in a row, which DOES happen). Plus, you could space the FPs out according to YOUR specific needs - plan them around meal, nap, and bathroom times - which is what this new system is supposed to do for everyone anyway.
Could this satisfy the masses (both disabled and non-disabled alike?) In my humble opinion, I think a system like this tied into the new FP+ system still provides reasonable accommodations that those who truly need them would still be thankful to have, yet it significantly would cut down on the "cheaters" from abusing the "instant & immediate" access they have now.