I Dont really think we need flash right now. I was really afraid of EG, i thought this is first step for MLP to became a girly stuff. You know, typical schoolgirs with magic, and ,ofc, every one of them is gonna get a boyfriend and so on and so on. And they will fight monsters every episode instead of finding what else friendship could be.
Im afraid that adding Flash will be a step into it. Girls will ask for more love lines, and main idea of Friendship will die.
I think they must find their love in very last episode. For a good end and good lesson.