since life support in the game isn't related to reality at all.
i say, why not have it augment radiation exposure and add radiation as an environmental attribute to both systems, stellar objects and planetary surfaces.
new suits could be created to handle walking
new srv could be created to deal with driving
Those "new things" would not require any real additional artwork or anything, unless they wanted to be a good gaming company and create some. But it wouldn't be necessary.
Then life support ratings can give you varying levels of radiation protection before your systems start taking damage from exposure. There would be no way to augment this with shields or other modules except module reinforcements to give the modules more HP's for the radiation to eat.
different levels of radiation can be given to different stellar bodies and thus systems. It also falls off in strength with distance from source of radiation (the falloff value will vary depending on the source and system, with some systems simply being flooded all over due to where it's at (maybe close to the galactic core).
Different planetary atmospheres can absorb different levels of radiation ...providing some local protection.
you could also use some planets as a shield if they aren't the source of the radiation themselves ...by hiding in the dark side for a bit.
Life support radiation protection would act kind of like shields in terms of how it behaves, where radiation is constantly dealing damage but the recharge rate of the life support radiation management can absorb that indefinitely if it's higher than the radiation rate.
But once it isn't, this capacitor will decrease at varying rates over time until it is 0. Once it is 0, you start taking damage. There is no way to charge this externally, you have to leave the system for one with less radiation or get to a place that is protected from it (stations, some planet surfaces, dark sides of planets or far enough away from the source of radiation that it drops below your life support max rating)
Boom, instantly you have a purpose for life support, you have a new environmental hazard to consider (fun), and new SRV (reason for multi-srv bays other than just being a bad driver) and new considerations for walking around. All with minimal effort from arts and design and other creative teams (unless they want to make it cool)
Bonus if while taking radiation damage, you start getting all kinds of hallucinations and red vision.