Wait until the changes are posted. UA won't do anything until then anyway.

You can ask UA to contact a *A carrier and ask it to open redemption space, but the chances of that happening are slim. There is nothing UA can do to force another carrier to do anything.

Presuming a "no" answer to the above, UA can force redemption space on its own metal and there are 8 daily nonstops SEA-SFO. Thus, while this adds a connection, the travel itself should be easy enough.

Close to a guarantee that there will be more changes.