The more I think about it. The more I honestly think I would have preferred it if Flash was more like Hans or a villain in general. Because:
1. It’d be a twist on the “Generic love interest”. Anytime the show defies expectations is awesome (Example: The reveal of the Changelings in Canterlot Wedding still ranks up as one of the best surprises this show has done)
2. A legitimate reason why Sunset and Flash were together at one point. (Both antagonistic characters).
and 3. If Flash was an antagonist in the movie, he’d likely have a much bigger role then he did. Cause he’d have to be defeated just like Sunset had to be. Maybe Flash’s role in this hypothetical version of Equestria Girls is he’s trying to get back in Sunset’s good graces by manipulating Twilight. And wants to rule Equestria with Sunset. It wouldn’t fix how stupid Sunset’s plan to begin with was. But at least THAT would be an interesting Flash Sentry.