Crazy idea here, but hear me out. It may just be the bourbon talking, but does the older footage need to be current? (I have no idea what the movie you're doing is about.) Instead of scrapping the already created footage, is there some way you can reframe it into a flashback, or a dream sequence, or use it in some other way that having a different look to it would not break the movie? You could give it a black and white or washed out look and use it behind a voice-over, etc. to fit it in between newer footage. Turn it into 1940s newsreel style stock footage or an artist's impression. That would give you a chance without needing to reshoot everything.