Roof replacement - plywood switch

After 20 years of faithful service, it's finally time to replace the rubber roof on my 1999 T-2670. I've kept up on the roof caulking, so there's never been any leak that I'm aware of, at least not noticeable on the inside; however, the black of the rubber roof is now showing through, especially in the area where the AC drips run out to the edges. Also, the rear of the AC is sagging a bit.

I spoke to a friend in the business about why my whole roof seems soft, despite no leaking, and he thinks this is a model that had Sunline's cardboard-like backing, instead of plywood. Years of snow weight, etc. stretch it out. He suggested if that backing were still solid, I should just apply a liquid coating since the rubber itself is not compromised. Otherwise, pull everything up, put down 3/8" plywood and new rubber.

I'm leaning towards the plywood/new rubber for a couple of reasons:

1. The overall "softness" is concerning, especially since I live in an area that can get decent amounts of snow weight on the roof.
2. The sagging A/C shroud is nearly hitting the rubber, if it drops further, it may rub/tear the roof. It seems like the rear support feet are falling between rafters, so plywood would solve the support issue.
3. Having a sold plywood roof would make future caulking maintenance, roof cleaning, A/C service significantly easier.
4. I would like to completely re-do the corner seam seals if I have to disturb them anyway. Some sections appear in worse shape than others as far as shifting, gaps opening, etc.

The biggest CON I can come up with, other than being more work, is the added weight, which being that high, could change the towing stability of the trailer, and obviously make it a somewhat heavier.

I'm looking for any feedback, suggestions, expertise, that any of you may have to offer.

Thanks!