The boarding system hasn't been implemented yet, but I think the addition of shipboard doctors would be pretty neat. As far as I am aware, currently the only way for crew to die is from damage to the power generators that keep the life support systems functional, or your ship blows up and everyone dies. However, damage to the ship's health should also have a chance to kill crew members, higher if the damage is to a crew compartment. Fighters that have been severely damaged but survive the battle could have wounded pilots. Damage to the engines could result in dead or wounded engineers. Destroyed turrets could result in dead gunners and miners. Damage to the hull in general would probably result in dead mechanics, who are ubiquitous throughout the ship.
A doctor could decrease the chances of crew members dying, or slowly heal crew members who are wounded. Or both. Higher ranking and professional doctors would obviously be better at healing crew.
There wouldn't be any need for fancy medical bay blocks and supplies and other overcomplicated things, just crew space for the doctors. They could probably fit everything they need in the crew quarters anyways.