Nah, don’t bother with all that. Just drill a hole in the floor (where your gas bottle compartment is, for convenience) and stick 12v split charge feed and 240v in the same hole. That’s how the ‘professional’ did my previous van anyway.Will paint the drilled metal entrance to the van to prevent rust and will use a rubber grommet and silicone to seal and protect the cable.
(One of my first jobs was to fix that I have to add!)