Yeah, sounds like a good compromise, given what you're building. I'd like to find a liftgate to put on the back of my motorhome too. Mostly so that I could use it as a patio deck, but also to carry dirtbikes when I don't want to haul a trailer.
I'm building my own, for several reasons:
1) Weight. Even the lightest aluminum rail-style liftgates come in at 1200lbs (for the largest platforms). And if you want a platform big enough for a deck, you have to buy a heavy liftgate (typically 1500-1800lb capacity).
2) Size. None of the commercial products are wide enough to accommodate the rear slide-out dimensions, so I'd have to have the fabricator cut up the rear mount plate. And the platforms are not bare-foot friendly (this I know from experience with our Thielman liftgate on the Funmover).
3) Malfunction. From personal experience, I can say that having your liftgate get stuck in the boonies sucks, since they're not easy to field repair and they don't have manual overrides. You basically have to take it off.
My platform will consist of two 4x8 structural panels and aluminum support frame, joined with a lock hinge. The lift mechanism will be my Rieco-Titan 5K lbs. rear jacks, which have several modifications to allow them to pull triple duty: lift and level the camper, lock the camper onto the subframe, and lift the cargo platform (folded). It will be able to easily hoist 650lbs (two heavy dirt bikes or dual sports, or one ATV).
Of course, the big down side of this approach is cost, since I have to pay someone to do all my fabricating. It'll suck if it doesn't work!