It might have been suggested already, but sometimes during playing or especially during character creation i feel like there should be the Constitution stat additional to the already existing stats.
I have no idea how much work that would require, but let us just have a short thought what could be influenced by the general constitution of a character:
Base HP of body parts and natural healing
Base Stamina and Stamina regeneration
Resistance against Poison, Radiation, Parasites, Food Poisoning, Illnesses and others
Base Chance for positive/negative Mutations
Also with the change of Bionics into a slot based system (currently WIP but looks very promising) it could affect how many slots per body part could be available for bionics or in other words how much of your body you can replace with other parts before your body functions get influenced negatively.
An another point would be that the Stats-Through-Skills-Mod might be easier to balance if the skills are influencing an additional stat and the stat growth is spread more.
There could be a reason why constitution is part of most role-play-games.