Per the MEA novel Batarians were on the Quarian ark. A Batarian could be a cool squad member but the reason for non so far is simple: they despise humans and dont want to work with them. Terminus armor and weapons would be cool.
The game is no longer supported so no dlc will be coming.
As for the Geth: no, just no. No more Milky Way stuff. Andromeda needs to stand on its own and people really need to let the MW go.
I heard scuttlebutt through a forum that EA was actually fixing Andromeda and possibly working on a Remaster of the Trilogy. I am an Alpha Level Xbox insider and can tell you this I have actually got updates for Mass Effect Trilogy and Andromeda. They have also been patch and fixing glitches and bugs. But can't go int anymore details than that because of Microsoft's Non-Disclosure agreement.
