if the Doctor succeeded, Deke as we know him won't exist in this timeline.

I have a limited tolerance for "Buffy sad, show good". If this show wraps without a HEA for Fitz-Simmons it's going to taint my memories of the great parts. or maybe I'll come up with my headcanon stopping point like I did for BSG. (It was a downer that the Cylons won. Sometimes I like to imagine that Adama figures out how to rescue the colonists, but the tragic end was fitting.)