Please don't put a bunch of screws through the side of that beautiful hull! Your idea has some good stuff.
Instead of screwing the 2x4 use epoxy glue to secure it to the inside of the hull. Epoxy glue will be stronger, look better and last forever.
You will need some framing from the bottom of the deck to the stringers for support of the deck and to keep the hull from flexing. You can also use 1/2 ply instead of 3/4, make the frames from 1/2 as well and you will shed even more weight.
The gunnel (gunwale) design you have will work great; but again, don't screw it, use epoxy glue.
I would cover the whole top deck with 6 oz biax glass for puncture and abrasion resistance then carpet it (if that's what you are going to do).
I am guessing it will never see planing speeds again? If so more frames will proly need to be added for the hull sides.
Just a thought: If this hull will never see planing speeds again I would sell it and build a displacement hull. With a displacement hull you will get better economy out of your electric motors (more run time), lighter weight and probably better overall speeds. You can proly build a displacement hull for what you sell this one for, have a better fitting boat laid out exactly how you want it.
I am not trying to discourage you from modding this one, just saying there may be better options out there for ya.
If you can give me some program notes (boat size, draft, overall weight etc) I may be able to find you a better hull to build.