thats almost exactly the way i was thinking, and i dont think i ever even touched a guitar in the 80's ;) .... although it didnt occur to me last night to cut the fret slots after the wood was attached so that going to make it a bit more accurate than i was imagining
i suppose the only real issue would be grain matching, since both sections of fretboard are firmly glued to the neck blank it shouldnt sound too bad. still think a full new fretboard would work better