That sounds like a plan.
Call me old fashioned but I think a huge hole in the floor needs fixing with some structural integrity.

 

If you are going to do it do it properly, I have done this many times and seen some really bad repairs done just to bite you in the *** later...

You start with this




Cut it out and dont be squeemish



Make a panel with a matching rib pattern and seam weld it in



Paint it, this car was changed to a dark grey so I used black



Then stick a rubber mat to it for good measure



A good tip... make sure you dry your carpet before you put it back as it will be soaked and will not dry of its own accord