Marty,
In answer to your question, in theory if you have large enough hands and long enough fingers, sure you could do it...but most fingerpicking tunes by Merle and Doc, lend themselves much more easily to a narrower necked guitar, because of the chord formations used. I'd say 1 3/4" nut would be about the maximum for comfort.

Keep in mind that Merle had a slim, narrow Bigsby neck put on his pre-war D-28 to facilitate playing. Whenever you see him in a video performing one of his classics on this guitar, it always looks effortless and he comes across as smooth as puppy shit. Part of it is his natural talent, and I would guess a good part of it, is also due to the slimness and ease of shaping those "Merle" chords on this neck.