Again, thanks everyone for some good suggestions. Nick, I'll take a look at EdiLoad and see if that can help us out. I'm happy to hear that Christian says that this workflow is appearing elsewhere... perhaps down the road there will be a single editing solution or workflow that solves all the problems we're having.
Although I have what I need, I'll try to clarify once more for Craig and Marc solely for their understanding.
Let's first consider how things are done in a recording studio, so let's say Marc is our singer and Craig is our engineer.
Marc is going to lay down a few base takes of his hit new single. These takes are continuous from the start of his song to the end. Then, because maybe his throat got dry in measure 25, he wants to re-record that measure and comp it in. So he does. And maybe he comps a few more measures, too. In the end, Craig bounces out a mix that is not just composed of the base take but also a bunch of comps - but together they add up to one full song.
In the audio-only world this is pretty easy. When Marc wants to go back and re-sing measure 25, Craig recalls the transport to measure 24 or so, hits record, and then crossfades the in and the out. Simple.
But how do you do this when you're also rolling video? You can't, because you just don't capture video into a 'comp' like you would audio. Instead, PT and cameras are rolling quasi-continuously through the entire session, and a producer sits there with notes to say "Let's go back to measure 25". Marc goes back and sings measure 25, which is not captured over the original base take but instead somewhere farther along in the audio and video files.
During all this, Marc's job doesn't get harder; he just sings when the producer or Craig tells him to. Craig's job actually gets easier, because he doesn't have to move the audio transport around as much.
My job, as editor, gets much harder.
After the session, Craig follows the producers notes and splices all the comps into the base take. In our example, he would take the audio at "Measure 25 Take 1" and move it to overlap measure 25 in the base take. That comp, which originally was in time with the video (even assuming timecode and tri-level sync for everything), has now been shifted somewhere else in the PT timeline.
So without a better solution, I sit there in FCPx scrubbing through until I find the video that was recorded during "Measure 25 Take 1" and then dragging it so it aligns with where the audio for that take is mixed.
That's the issue we're having. I'm not sure if I can be more clear than that.