That's certainly an interesting and ambitious idea! However, I think doing that would completely throw the balance off. If you give characters like Baraka, Nightwolf and Frost the same kind of 9-frame mids that Cassie and Jacqui have, not only do those characters become obnoxious now, but it takes away from the unique utility that a character like Jacqui has.
The rest of the cast besides the top 10 or so are fairly well-balanced, except for Kotal and Kano. If anything, I think those kinds of mids should be rarer, that way when a character has one, it's a big deal. And they should work in the same way that the characters with 6-frame pokes do - they are the fastest pokes in the game with some of the shortest range and can be low-profiled.
Now, if you're talking about giving these characters the same kind of 9-frame mids that Kabal has, then I might be able to get behind that.