With all the different shapes already in play and with more different shapes to come with the modeling, it may be easier to replace static animations with inverse-kinematic (IK) skeleton animation. (This game might never support IK, but it might add to the immersion if astronaut physics were as intricate and interesting as ship and asteroid physics.)
Sitting example:
Set the bottom of the torso a.k.a. butt on the sitting point. If it's a half-slab or less, or if it's a downward-angled surface, put the thigh bones out straight in front of the body with a 15 degree outward angle on each leg, then just swing the feet down to wherever they touch something. Otherwise, angle the thigh bones at a 45 degree angle from the torso, and then swing the feet down until they hit something, ignoring any block that is in the way of the "feet" when they are first calculated.
Usually, you are not sitting during a major lag moment, so the extra skeleton calculations shouldn't add too much lag.
Subtle but easy "personality" setting: preferred thigh angle when not sitting in a "chair": Maybe I would prefer and could set a 30 degree shallow thigh angle, while maybe you would prefer a 60 degree thigh angle. Each player could set their sitting style, so everyone could sit differently on the same entity. It would be a subtle effect, but would effectively multiply the number of "sitting animations" available to the game. If the setting is easy enough to get to, you might regularly change your "sitting style" during a game session.
Another fun feature of IK skeletal animation: If a player gets hit with an explosive, but doesn't get vaporized, they could be thrown like a rag doll. When dropping, whether from being thrown up into the air, thrown into a wall, or just being shot with a non-terminal "bullet" or "laser", the astronaut could be laid out on the floor in an infinite variety of patterns, depending on the angle and location of the hit, their current animation, and anything else that might involve the astronaut skeleton. When skeletal animation was being introduced into popular AAA games, the old static animations were derided as old and broken and immersion-breaking. It's now considered standard-best-practice to use skeletal animation to properly drop a body on the floor. Static animations are laughably old-fashioned now-a-days. (But static animation is still found in some games, because IK skeleton animation is relatively difficult to understand, versus modeling a standard falling animation or three.)
