*EDIT* Should have been more cleared in topic... first leg of the *return* trip, not the outbound!

Have my end of year MR booked and ticketed, but am thinking about a possible schedule change.

Now, I am thinking with the change fee it might be just cheaper to book another separate (UA) one-way to my connecting city (SFO) and pick up the return from there.

Is that possible, or will they cancel the second leg of the return?