I think from what you've described you are well ahead of the game.
Tabbing in all the frames takes a long while and it sounds like those are mostly intact. Yes, butt joints will repair the hull panels. I think all of us used butts joint on our hull panels, as I don't know of any plywood 18 feet long

....some may have made scarfs but that's a lot of work. Incidentally, there's a video somewhere on line where a guy shows how strong his butt joints are related to boatbuilding. He basically torture tests the small panel he put together and the plywood gets destroyed while the butt joint remains intact...so I trust this method of joinery. You can always sister another piece of ply on to anything that seems flimsy, there are some placces on my boat where I did this.
So, yeah! Resurrect the Elroy! Are you in Savannah? I can't remember where you said you are located. Send us some pictures! and best of luck, too.