A panel in an RV is no different than a sub-panel in a house. It requires a ground conductor back to the main panel where it is grounded. A GFCI recept. or breaker cannot be substituted for the lack of a ground conductor to a sub-panel - no exceptions except in old houses with existing 2-wire recepts. with no ground wire. The ground connection in downstream/sub panels cannot be bonded to ground and the ground conductor needs to be correctly sized. It is unsafe to have an RV ungrounded.
The existing work sounds like a total mess. It's hard to give good advice from a distance and there could be other related issues too that should be dealt with. Short of completely redoing it, the easiest solution sounds like converting it to 30 amps (120 volts) and re-identifying the conductors with the correct color tape per NEC requirements.
Ground requirement for RVs (and RV Parks) is covered by art. 551 in the NEC. For some reason I can't find the free online 2104 NEC otherwise I'd post a link to art. 551. For accurate advice, the Mike Holt electrical forum is good. If you don't have a good grasp on doing electrical work and don't know the code requirements, I'd hire an electrician.
