I think that NiMH batteries are also not that far behind dynosaurs ... didn't they fall out of favor for cordless small hand tool use some time ago? Some form of Lithium seems to be where it's at nowadays in contractor cordless hand tools (... and of course for electric vehicles, too).
Marine Batteries are basically a deep cycle start battery! In other words they have the bad characteristics of both a start battery and a deep cycle! I would stay away from using Marine batteries in any RV situation. Number Two, if it has Cold Cranking Amps in any part of its requirements it is NOT a Deep Cycle Battery! If you use AGM type batteries check your charging system to make sure it is compatible.