O'bob-

If that Italian 410 was new and cheap enough, buy another one just like it and have a 2-barrel set.
Don't move the firing pins at all, just set the chambers of the rimfire down juuuust enough to have the strikers hitting the rim of the case, not the center.
All that's needed there is eccentric turning of the barrel journal, then a more judicious job of barrel striking once all's screwed/soldered together.

You'll likely have a wee bit of barrel/lump fitting to do to get both sets of barrels fitting up properly on the same frame, but you'll end up with a 22 AND a 410 double, in a switch barrel set!

Then once you're done you can sell the other stocked receiver on gunbroker (or whatever) as a double rifle project ready-to-go and you'll likely get back most of what you paid for the whole gun in the first place...