Well, usually I do the amicable thing and respect that everyone can feel any way they want about Flash. That said, I actually don’t like Flash the way he is. As a tool used only for romantic interest to Twilight. He needed character.
So instead of griping about how flat he was as a one-shot character, I made him charming. I made him bashful. I made him timid, but always putting his friends first. I’m okay with him being the love interest where intended to be (some folks have/will have problems dealing with that should it actually become something more than Equestria Girls canon).
I have a writeup about my head-canon and attitude towards Flash Sentry. http://tmbr.biqbox.com/post/79729031729/the-deal-with-flash-sentry
What I’ve done has turned a few heads in the community and more than a few have changed their perception about him based on how I took the blank slate that is Flash Sentry and ran with it.