I thought about putting heavier character ties in MASHED, but in the end I went with simple Hx. (I couldn’t very well ignore it anyway since “Hx” is already a medical term!) In the game, Hx is a mechanical and story benefit, but not one that (I feel) would be a disruption if the person you have Hx on goes away. The game also indoctrinates you into Hx being fluid, since you change how your Hx works with two other Roles if you end up changing our own Role.

Of course, I benefit a lot from the setting and the episodic nature of M*A*S*H (one of the main inspirations, natch). You can easily excuse a character disappearing by saying they had to hop in a jeep and go to the front or maybe they even got transferred or sent home (eg., like Trapper did in the show). Then the CO can make a hard move to give the remaining ally Stress to try and deal with the loss.