Mini Split AC - Condenser unit in fifth wheel basement??

I would be concerned about the added heat load to the camper. Along with leaving the access door open, you may need a fan to force some air movement. I would also caution you on draining the condensate to the sink drain. That is going to add quite a bit of water to your grey water tank. If you camp in a hot humid place without full hookups, that could be a problem.

You may be onto something, keep us updated as to what you find.