Google Voice landline port: can't but have an idea

I've had my landline number for a long time, but I'm ready to cut the cord. I bought a small Obi device and tested it using my Google Voice number. It's pretty good! I'd like to tell my phone company to end my landline service, but I'd like some way to port the number to a new Google Voice account. According to GV support pages, it can only port mobile numbers, not landline numbers. So, here's an idea

I choose a prepay wireless plan and tell them to port my landline, ending my landline account. I can use an old GSM phone with SIM card that I have laying around to do this, I think. Now that the number is a wireless number, Google Voice should be able to port the number. This will end the prepay wireless account, which is fine because I think I can find one for as cheap as $15.

Has anyone else thought of this and tried this? Is there any reason why this wouldn't work?