Eren Yeager – Todd Haberkorn (could be great or could be a disaster, depending on how he decided to do it)
Mikasa Ackerman – Brittney Karbowski (a surefire win)
Armin Arlet – Josh Grelle (Armin needs a voice actor who can pull off major cowardice)
Levi – David Wald (a pretty good bet methinks, but a lot of other VAs could do Levi well)
Annie Leonhart – Brina Palencia (another surefire win)
I like your choices for Reiner, Conny, and Jean.