Why just keep Barry, Caitlin, & Cisco as your core three. Keep Joe as the only West allowed in Star Labs. Send Wally off to Teen Titans show that's being developed right now. Make Iris do investigation for the newspaper.
Since Caitlin is full blown Killer Frost now, I think Tracy Band will replace her as the new female scientist in Star Labs heading into season 4. Even if the team finds a way to fix Caitlin's personality disorder from her cold powers, Caitlin will be ashamed that she hurt her friends and will want to leave. I'm sure we will see a lot more Gypsy in the future as well.