F5 i-series Guests to r-series tenants migration

Definitely option 1 is your best method.
Did something similar but as said here if you can put new self IP's that will be a lot easier.
If you are in a production enviorment and configuring the same self ip's just remember to shut the ports towards the new machine before actually connecting it to the enviorment so it wont cause any issues until you are ready to add the new one.