It is necessary to have a generator in a 5th wheel, I know some have them some don't. We are looking to go to a 5th from our class a and we really don't use ours a lot now.
I have a DuroMax XP4400E generator mounted in the front storage compartment of our 5ver,I ran exhaust piping out the bottom which exits behind the left front jack.
I also mounted a 50 amp male plug in the compartment wired to the electric panel.I can connect it quickly with an adaptor.The generator gets used occasionally.
Generators are nice to have... just like 4 wheel drive and a 12k winch.