There's a good chance I'm making this more complicated than it needs to be. Background: I'm Marriott Platinum and Southwest A-list preferred. My southwest companion pass expires 12/15.

I'm thinking of using my Marriott points to book a travel package of 7 nights +110,000 Southwest points in January in order to renew my companion pass as quickly and early as possible. My concern is if I wait to book the 7 nights, the hotel may be sold out.

Can I book the hotel now under a cash stay and then switch the reservation once I'm issued the certificate?