I don't see why it wouldn't work.
Just keep in mind that you'll have a lot of heat dissipation out the back of the unit. -Don't box it in too much.
Some of the smaller AC room air conditioners are very energy efficient, and even the smallest in terms of BTU will probably freeze you out
And at maybe 1/3rd or less the cost of a RV unit..
Make the mount hell-for-stout, Ken.