I think everyone appreciates your suggestion and I can tell you put a lot of effort into it just want to advise on the cut out what isn't structural part. Its difficult for people without diy experience to tell what is and isn't structural and something like this should probably be stripped of drywall and subflooring then temporarily supported from below while the rot is removed. That can be very overwhelming for a first timer. Just make sure someone around knows what they're doing at least somewhat before you start removing and beams from the floor, even damaged ones.