Well I gave them a call.
Said the only FRA-SGZ flight is at 5 PM, the previous one at 1 PM is gone.
So I asked if they could route me through MUC or maybe LHR rather than FRA.
No dice. Sounded like they could open up SFO-FRA direct, rather than my going SFO-YVR-FRA. Maybe I should ask for that anyways, because while the LH 350 was okay, I didn't like the 2-2-2 config, though I had the two seats to myself.
HUCA?
UA can not open up partner space, so any reroute would require partner space being available, HUCA will not change that.
So yes UA can open SFO-FRA. They could get you to LHR or MUC also but how would you get to SGZ, UA can not help with SGZ beyond what has existing award space.