The only issue with scan is that (if our data is correct) it will never match a live recording to the original album version, because it's looking for the exact same audio.
With lookup if the track name doesn't have 'live' in it, and you clear the album name tag, it should be searching for the original release group as well as all the others.
Actually... I just realised that you probably figured this out!
Yes, doing that and then running it through lookup with the sliders changed should work pretty well!
One note is to please not hit 'submit' in picard when using acoustid with these tracks, since you're not trying to match the technically 'correct' track, and it will save incorrect information to MB.
Oh and other note sorry - since you're working with individual tracks, and you don't necessarily want them tagged 'correctly', I'm not sure if Picard/MB is the best tool for the job. There might be other taggers that are much more basic that do better at just throwing out the original release and nothing else