Honestly speaking, I'm fine with Flash Sentry and Twilight Sparkle as a canon ship. The team who are working FiM could make it work while still keeping the show focused on the Mane Six, you know a ship tease here or there, a lesson on not forcing friends into relationships they're not ready for (Either a Rarity or Pinkie Pie plays matchmaker episode). You know make the romance secondary, subtle and more importantly develop it from friendship first instead of "Here's Flash Sentry, he's definitely gonna go out with Twilight" and more "Here's Flash Sentry, he's friendly with the Mane Cast so we'll see where this goes." IMHO
Even then, even hinting it would cause chaos in the Bronysphere, but let's be honest it would be like the sixth overblown s**tstorm to hit the fandom.