I'm just talking out my butt here, but I bet just a coat is all that would be needed. I also think it would help to make the jacketed bullets .001" larger than groove diameter to start, and keep the jump to .010" or less. Start with a stripped-clean bore and swab some BLL in it before starting. Give it 50 shots to fill the holes back in and I bet it doesn't copper foul any more.
I can see abrasion fouling happening, but lube tends to help that out a lot and keep it from accumulating when it does happen. But where is the most copper? In the corners of the grooves (trailing edge, where the gas leaks), tops of the lands where the rough drill marks are, and anywhere else there are chatter marks in the bore, right? So we're seeing (presumbably) the effects of gas cutting and abrasion fouling with gilding metal jackets. Seems to me that fixing the leaks with fit and putting a little dynamic film slickum in there would fix both problems. I understand that jacketed bullets tend to "slug up" once engraved due to having no grooves and the displaced jacket material having to go somewhere (grooves), but I still think the jackets are too hard to keep the dynamic seal intact as well as cast bullets do in anything but a perfect barrel. Ever notice how hand-lapped barrels copper-foul a LOT less than cheap production corncob barrels do? I say better bore obturation and less jacket abrasion is the reason. My Rock Creek 5R hand lapped .308 barrel came to me with 400 rounds of jax through it without any cleaning and try as I might, I never got any green on a copper-solvent patch.