If not a true take down, theres allways the switch barrel way. The same contur in the barrels and add a lug or similar under the chamber allowing you to have a custom spanner to unscrew one barrel and turn on another.

If i understand it right you wont use both when on hunting so theres no need for a second shaft or the take down mekanismen, you would have to have two scopes and check for zero everytime you change barrel anyway.