1972 911 battery mount

So the "blind" nut that holds down the driver side battery mount has corroded, and some idiot broke the "blind" nut loose (NOT THIS IDIOT!!!! :)).

There is no access point from the underside or anywhere that I can find....????? :confused:

So either I cut it off, and let it rattle around.. :( And install a "rivnut"? OR take a hole saw, remove it, install/weld in a new one and weld the hole back up. :confused:

Thanks for the help! :)

I use a 8 X 1.25 13 mm wrench size flange nut, turn it flange side up, and mig weld it in. Grind the welds down and you have a new captive nut.