So recently I got interested in White Star, a science fiction retro-clone based off of 1974 version of Dungeons & Dragons. It's been a popular game for nearly a year now in the OSR, and spawned a lot of compatible third party support. At a whim I snagged up several of them, one of which is Five Year Mission, deriving heavy influence from you guessed it, Star Trek.
Many of the new classes are geared towards archetypes from the show, but the one which stands out most to me is the Expendables class. You might find it an odd choice to have red shirts as a playable option when you have ones geared towards specialized important roles such as pilot, engineer, guerilla, and so forth. But the interesting thing about Expendables is that the player who chooses this class controls multiple characters.
Basically, at any one time there are two Expendables in play, with the rest being controlled by the GM and assumed to be off-duty or awaiting orders back at home base. They all share the same experience points, hit point totals, and game stats, although conditions "in the field" like lost equipment and damage is tracked separately. When an Expendable dies or is permanently disabled, another one comes into play at the earliest opportunity which makes sense for the plot. However, PC "death" is still possible if too many die in a short amount of time as they run out of troops.
Beyond just being easily replaceable, Expendables can buy equipment at a 2 for 1 rate at character creation and are capable of taking a blow for others by interposing themselves between an ally and impending attack as a reaction to said attack.
They remind me a lot about the concept for Hirelings, except that they're directly PC-controlled and thus don't have things like morale checks to worry about. I like the idea, although I get the feeling it would be a hard sale to many players, especially given the fact that it may be a less attractive option than picking an individual named character with the special abilities of other classes. And in games which have a heavy amount of role-playing and character development (a likelier scenario as PCs climb the levels), it may feel odd to not have a single person to control in the event especially when said Expendables may very well die unceremoniously. Still, you don't have to worry as much about character death, and having 2 PCs at once can be a viable option at low levels when things are overall deadly regardless of character class.