[@BCTheEntity] Something to keep in mind is that all the various implants and additional organs added to a space marine aren't natural. As marines can actively control most of them, that means they have to be artificially attached to the brain. In addition to the various tech-marine implants, there are a Ton of injuries that a marine could receive that would require open access to the brain to fix. There would be various machines and what not that could, in theory, bypass the need to look at the marine's brain the old fashioned way, but I doubt a scouting vessel would just have that kind of thing on hand.