I would try and make it waterproof first so pin all those wires up to the inside of the deck put the boat on its trailer as a jig to keep it straight and start lightly sanding the inside of the hull up and hoovering up dust as you go (wear a mask) to give a clean substrate for the epoxy to stick to on the inside.
Three layers of matting to reinforce the effected areas that leak should do .
Then you will need to glass in some new hardwood cross members to fix the floor to.Use a levelon these and place @ at 2 foot centres then 3/4 inch ply on top of the cross members leaving a hall finch gap around the side you can use a cardboard piece for a template.
Then fibre glass the ply on top and to sides of boat.
Cover with carpet.
Decent battery box in ply and fibre glass and fit out.
You might want to glass in a couple of Hard wood cross members on top of floor to fix the seats to either by 1/2 stainless bolts or coack screws with large penny washers
Good luck !