[skidlids]

Nat the sleeve on the threaded collar is only about 12 to 15mm long.
I would attack it from the chain side, drill the top of the allen bolt off by working up to a 10.2mm drill. Then it's a matter of drifting the whole lot out.
Trouble is the steel bolt passes through four tight fitting collars, two on the ride height rose joint and two on the shock. Lost and lots of release agent required.