Update...it worked. Had to do it with CSR, but just booked:

DEN-SFO (Q) Refundable
SFO-LAX-MCO Quap-(A) first
MCO-DEN (E) Refundable

all on same itinerary. It took her some time, but she pulled it off.
All fare rules allowed combinable fares. But the whole itinerary is subject to the most restrictive fare. (In this case not a problem with the bookend refundable/changeable fares) But if you did book a non-refundable on one leg, the whole itinerary, including the (A) fare, becomes non-refundable.

Thanks for the tip! Saved me from booking 3 one ways on .bomb