Well, this got a little heated after I last posted.
Quick update - we got together for one final session with a fairly short to-do list, with this being one of those items. My uncle practiced his ass off, and delivered maybe 3-4 pretty good takes, out of which I was able to comp together something that was quite a bit better, both in performance and in audio quality, than the original I'd been struggling with.
The Spectral editor is a pretty damned cool tool, and while this particular track has been on the backburner while I work on drum sequencing for the others (I had shoulder surgery in January and then I'm just getting to the end of cycling season, so there hasn't been much progress here since then aside from that one session where, thankfully, I didn't have to play all that much myself, just run the recording process), I may have still used it to clean up one or two errant sections. But, for the most part, I was able to get a good enough performance in tracking that it didn't require much work afterwards.
Since we're getting into the philosophical side of this... I guess my attitude has always been to completely separate the recording and the mixing sides of the process. While wearing my proverbial recording engineer hat, I'm a complete nazi about getting the right tone, the right take, the right performance, the right vibe, whatever, and going at it basically as if there's no safety net, and you have to get it perfect up front. Then, when I switch gears and put on my proverbial mix engineer hat... The sky's the limit. Spectral editing, slip editing, comping a performance out of several takes, whatever. The only place I tread a little carefully is anything manipulating the lead guitar performances since I primarily write and record instrumental guitar material and for a variety of reasons but not the least of which the fact that digital recording has led to a LOT of artists releasing music they can't actually perform, but even then I'd be lying if I said there weren't a handful of notes that i shifted a few miliseconds one way or another on my last album, because they were just slightly out of the pocket in a take I otherwise thought something pretty cool was going on.
Idunno. So, I think you can definitely go at it both ways... But, that becomes harder when you're not yourself the artist. For me, it's a simple matter of either re-recording the part until I get it right, or if I can't, simplifying or rearranging it into something I CAN play... But, when you're recording someone else and you've got a one-day session to track a couple songs, you can ask people to have their parts down cold in advance, but once the red light is on it's out of your hands.