Of the mid-season finales I've seen (Arrow, Flash, Agents of Shield), I liked Arrow the best. They seem to be the only one to really go all in for the big cliffhanger.
It will be interesting to see how it plays out. I'll admit Felicity is still my favorite character on the show. My favorite scene was the interaction between Felicity and her Mom when her Mom finds the ring.
Still, the show is called Arrow, not Felicity (damn, if only the actual Felicity show had starred Emily Bett instead of Keri Russell and had been fun instead of continually depressing). It probably would be most appropriate for his story arc if she actually died.
I could certainly see leaving her dead for awhile like they did with Oliver last year.
Oh, and the plot line I would like to see: It turns out that Rip Hunter from Legends of Tomorrow is actually Felicity's father, but becoming her father is still in his future. So he has to travel back in time to become her Dad and then also uses time travel to save Felicity after she dies (I sure he can do wonders with access to 41st Century technology.)