Sheared captive nut options?

[JB21]

Ok so pulling the rear swinging arms off my Celica I've managed to shear one of the three captive bolts on the off side.

You can see the old nut and part thread were I've cut it and its now rattling around in the box section.

So i could drill/cut the centre hole as this doesn't have a bolt and is just open and remove the old bolt. Seems pointless though as i won't be able to get hold of the replacement nut to tighten in the new bolt?

I could also tap the broken bolt hole but again seems pointless as the metal is to thin.

So my question is could i have a flat nut welded on the out side of the box section to thread my new bolt in? Or is this just poinless again?

Any other options?

 

[JB21]

Sorted.

 

[bloke]

was going to ask what's on the other side? boot floor?

 

[JB21]

Its where the boot floor starts the fold up so not really accessible.