Really all you need to do is accept the Digital workflow and buy as much capacity on a firewire drive as you can . I’ve not had a problem wit batch capture of a whole full tape with no gaps . Plug it in and start it and go away for an hour . Then you have all your media on your computer and you can manage it all there and do what you like with it. Drive space is getting so much cheaper now it’s the way things are going.
Having said that I can understand the hassles post houses and such might have with HDV , it doesn’t want to play the way they want to play , so they fear change and say " it’s crap and it don’t work "
HDV takes up no more drive space than DV , as a matter of fact if you shoot HDV and convert it to DV on capture it takes up more ( slightly) than if you leave it in HDV. Remember they both fit on the same Tape !
I was thinking again earlier about your predicament and I think that you’re probably going to have difficulties because you will need a new blank sequence set for HDV to import the footage into. But you can copy and paste all the effects and transitions from one timeline into another so you might want to maybe try and get FC to capture the HDV footage you want first , drop those clips into a new timeline ( So they’re cut the same ) then copy all effects transitions etc from your original cut to the new timeline. I would however leave the colour grade till last and do a new colour grade for the HDV .
( I sound like an expert here , But Dan is the man really , I glean a lot from him on this stuff )