For convenience (and maybe per ABYC) there needs to be a disconnect switch. Otherwise you would need to unplug shore power to work on the electrical system.I believe you can bring 4 wire 50 amp service onboard & split the hot legs at the plug. But I don't have the standards book to verify
Oh, also, the aircon units probably need individual breakers (have to read installation instructions). So a second AC panel would probably be needed regardless. With a main switch and however many branch circuits are required. Maybe it could just be a 30 Amp pane if that is enough for the loads.