Ok, so I'm considering starting up a Fallout Equestria side-fic after the train-wreck of my previous fic (Harsh critiques basically killed any motivation I had for writing it any longer) and I've got an issue.
Ok, you have two of the main characters, Midnight Strings (A male cyberpony Unicorn musician) and Desert Rose (A female "earth pony" dancer and entertainer) were previously in a relationship before they decided to break it off under civil terms. They still care for each other, but less in a romantic way and more as just good friends. At some point in the story, they (along with a third as yet unnamed character) get captured and drug into a Changeling Hive (Changelings being insect-like shapeshifter ponies that feed on love of all things). Anyway, Strings gets out and murders his way to his friends (He's initially a hydromancer, but the Hive forces him to adapt to use blood and ichor).
The question is, should Desert Rose be replaced with a Changeling? I can't see of a way it would further the story other than letting the readers keep guessing until the reveal. Maybe once the secret is out it would allow for different methods for combating enemies?