We've also had problems with Universal - that's why we have not been there in about 6 or 7 years. It just was too much hassle. There is more to accessibilty than just not having stairs.
It sounds like our families needs may or may not be well addressed with the new GAC. It's not easy or fast to get a totally dependent, multiply disabled teenager ready quickly in the morning. And some days, she's just pretty much non-functional all day (like a big rag doll with her head lolling and no energy. If we get to the parks at 11 or after (which is pretty much average for us), many of the popular rides don't have any fastpasses left or they are for the evening. That pretty much means we won't get to ride because we can't get there early enough to get a fastpass and if we do get one, it's so far in the future that we might have to leave before that. Or, if it's a ride we have to lift her into to tranfer to the ride seat, we may be too tired to be doing any more transfers. And if we have an unused fastpass, we won't be able to get another one for quite a while. We didn't usually use our GAC that often, but when we did, we really needed it.
The alternative entrance message in the past was mostly to let people without wheelchairs use the entrance that is wheelchair accessible (which is occasionally the exit or the fastpass entrance, but would usually just be the Mainstream line). If it stays that, we would already be using the alternative entrance because DD has a wheelchair, so all we could get is the stamp that allows us to wait out of the sun. We've had that stamp before and it didn't help a lot - we still had to prevent DD from hitting people in line (she's impulsive and likes her personal space) when they cut her off, let their kids run their fingers in the spokes of her wheels, and (my personal favorite) encouraged their toddlers to sit on her footrests, on top of her feet.
Anyway, we'll see. Some of the stuff (like the easy to interpret icons) should be very nice.