I have seen enough to know that a decent machinist can do pretty much anything with metal, short of converting lead into gold
using a standard 10/22 barrel, I'd guess an offset sleeve would work easy, if the stub hole is too large.
if the stub was from a smaller diameter cartridge rifle barrel, I'm sure an offset hole could be bored.
now, if using a large diameter aftermarket barrel, I think a rifle barrel stub would be the easiest option. as a sleeve would run pretty thin.
Might be easier to modify the Firing Pin to accommodate the RimFire.