I had an award ticket for my father (no status), but booked with my miles where I wanted to do something similar. He was flying MCO-ATL-JNB and he had an 8 hour layover in ATL. Changing the domestic flight changed the one-way award from something like 80k miles to 220k miles. The day before the flight I asked if he could leave in the afternoon instead to shorten the layover, and the agent did make the change without penalty. I think your best option is to explain why your circumstances have changed and hope to find a sympathetic agent.