that seems like a good approach; assuming there's an easy way to set up new mac and enroll it in beta program
This should be easy enough. If this were me I would personally set up the new Mac as a "new Mac" (no migration), using a temporary account that you plan to throw away. Then, upgrade it to the same (beta) version of macOS that is on your current Mac. After that, use Migration Assistant to move over your stuff and your "real" account, then delete the temporary account.
If you can wait a bit, macOS 26.2 final should be out in mid-December. It'll be a little bit less hoops if you don't have a beta OS in the loop.