Good digital pianos are not real ones; I very much understand that. I in fact have a (old and slightly decrepit) baby grand in my living room. However, the better digital pianos nowadays with some of the graded weighted hammer actions come remarkably close, in my opinion. For that matter, as you undoubtedly know, there's a good bit of variation in how different acoustic pianos play.
Besides the obvious tuning issues, I'd be worried about the vibration causing no end of minor difficulties with the action, bits of it working loose or getting out of position or generally needing a good bit of regulation with each tuning. If you know how (or are willing to learn how) to do tuning and such yourself that would probably work out to be a substantial savings in money. At any rate, if you start out with a very good upright it will not remain a very good upright for very long, I suspect.
If you do put an acoustic piano in the motorhome, try to have its weight as centered left to right as practical. If it's against an outside side wall, it'll be quite a bit of weight that's not balanced, and that tends to be problematic. Also for sure make absolutely certain it's well secured. It would be advisable to avoid having it in the back as there's more bouncing there than towards the middle.
It would probably also be a wise idea to make sure it fits through the entrance door, which is usually quite a bit narrower than most house doors. Sometimes large items (such as a replacement fridge) are put into or out of an RV through a large window opening, after removing the window, if they won't fit through the door, but a piano won't fit through most RV windows.
Please do give a little more thought to a digital piano. It would be a whole lot more practical in this case.
