The ONLY way to do this right at this point will be to hold elections again in contested states. No mail in or other fancy options, not even for the military.
We'll need enforcement of laws, with arrests, and jail. Of course, arrests to be avoided if people just don't break the law by cheating.
If we're not strong enough and willful enough to do this, then, I fear we're not worthy of our American country and values. And, where oh where is the FBI...again? If 15,000 ballots all come in for one candidate, yeah, I'd want to know if there were 15,000 sets of different finger prints. And, if not, well, whose finger prints are there? That person should sit in jail until the END of the NEXT presidential term.
The time for philosphy has past. It's time for action if we have that much backbone left.