I agree with Zath, base defenses weak and they should have overall better stats. Also a major buff to wall turrets as well, with all the upgrading they need and research they should be a more powerful defense and perhaps used in overall defense rather just last unit to defend in a defense. Also i know some may hate this but what about a slight nerf to shields. They should a cool down timer and not just be able to be activated seconds after the last one went down.
-Black Heart Forumer