If you can't or don't want to drill out the rivet........here's a wild idea: drive the threaded arm into a most forward possible position and have a tig welder lay a bead all around it on the back side.
If necessary then dress with a dremel. I've seen some pretty dadblame well controlled bead lines by good welders.
I've got a friend who came out of the nuclear reactor construction industry. He can weld a set of cuffs on a mosquito's ankles. Litespeed is also in my town and has some pretty good graduates.
There must be others.
This is a "disposable" crank at this point. You can't mess it up any more, practically speaking. Have some fun. Think artfully and maybe put it back in service.