I discovered by accident a while ago that it is possible to circumvent the room preference restrictions that exist for some online reservations (especially reward reservations). If you call to reserve a room, the reservation agent is able to put down your preferences and note a room upgrade request as well.

I have been able to request a king bed, high floor, ask for a refrigerator and a room upgrade on the phone when the online reservation will not allow any of it. The king bed is confirmed and everything else is subject to availability.