Steve,
That's an interesting thought. I suspect that it could be done and it could theoretically be totally fine. For me, the question would be answered by; "would this pass tech inspection at the track?"
And...what are you epoxying to? You'd be putting a lot of faith in the previous owner's repairs.
It sounds like you love this car and you're investing money to make it better...I would encourage you to get some quotes on welding in a proper floor pan or having the previous repairs corrected with actual metal and weigh that against the risks and variables that go along with the epoxy idea.
Purely my opinion.
