Looks like a solid plan to me. I was going to ask how you planned on adding the Encode, but apparently you found a community driver for that. I was also thinking LCM might let you just keep a code around without being assigned to any device, but it doesn't seem to allow for that. So, that looks like the best option to me.
"Swap Apps Device" would be another if you are adept at removing dead Z-Wave nodes (or could power the lock back on after removal to exclude it normally), but since the above is easy enough, I don't see a reason to risk that.
I would go one step further. Create a virtual lock and call it temp-lock. Then use device swap to swap it into all your rules. Go ahead and remove lock. After you onboard the new lock, device swap again. That way you don't have to fuss with your rules too much.