On flights where I have to work, having the extra tray table and empty seat helps me be so much more productive by spreading out, having a surface to use my tablet as a 2nd screen, etc.

Maybe this could be another use for our generally useless PlusPoints on flights where we're not going to be upgraded. For xx number of PPs, the seat next to me will be blocked unless sold or filled with a standby. That seat will be filled in reverse order based on the same factors as upgrades (e.g., the seat next to a Plat would be filled before the one next to me (a 1K), which would be filled before the one next to a GS). That way, it's no longer at the whim of the GA or FA.