Small boarding idea, but just a small list of a few things you can include alongside the up and coming boarding update. I can elaborate further on each idea, just ask :3
Security posts. A single block that allows you to station or "promote" one or two crew to security guards, sporting better weapons and armor, and is a sort of way to keep your guards evenly spread out. Maybe make it a sort of addition to a corridor to act as a check-point, granting cover to said guards as a means to hold back an offensive and provide fellow crew time to prepare a counter-offensive. I guess you could also just make this idea into a sort of "Secure" function for certain building blocks like corridors, command posts, reactors and such. Basically, a way to secure the inside of your ship and its most vital parts. (I know this may fall under specialized equipment for troops, but its an idea to add to that.) To balance this a little, seeing as people would just fill their ships with these most likely, make it so you can only have them 3 spaces between each other.
Another idea: Morale? (This one is a VERY BIG MAYBE) The ability to take over ships with sheer morale loss, forcing the rest of the crew to fall to your side. I feel like this would be a fun way of gaining crew in Career mode, as well as a fun way to commandeer ships. Granted, this can be very overpowered, so i think a way to balance this would be to add criteria before a ship can be commandeered through morale loss. This would be: A loss of 75% of crew, The complete loss of all designated security personnel (Optional), and of course full loss of the command rooms. I also feel like this would solve a problem of needing to hunt down every single individual resisting crew member.
(I will add more as i go)