captive nut repair question

[thejimrose]

anyone have any clever solutions for a broken off captive nut?

one of the captive nuts broke off on the a4 upper rear shock mount. so
i'm looking at a piece of sheetmetal with a hole in it and no way to
get behind it to get a nut back there.  it's some kind of sealed
cavity between the c pillar, trunk, and fender.

i think id have to have a panel around the hole cut out, a new nut
welded on and the panel welded back into place?

tia
jim