As a little feedback, I've been exploring Gremak strategies lately. Slavery seems difficult to use without upsetting many non-Gremak populations in your empire, but I think I just need to be more aggressive about making Mauraders to keep the peace, and 'using up' slaves when I have too many.
Horrific acts aside, back to boarding - Gremak seem extremely well suited to boarding, especially in the early game.
Their ships have Distortion Fields, allowing them to close to boarding distances without suffering too much damage. They struggle with early research, meaning captured pirate or enemy vessels usually provide huge boosts to scientific progress - and using boarding pods over a medium weapon is hardly a great loss when you don't have many good weapons available to put in there. And their Command Cruisers and Battlecruisers have Assault Shuttles, allowing you to continue the process.
Also, there are various documentation issues I'm not clear on - Assault Shuttles indicate there's a penalty for landing ground troops that they remove, but I'm not clear where this penalty is (or if it exists at all).