i feel this should be base game....

I definitely like this. Rather than a grenade I think I'd have gone for slight durability, but perhaps that could be added too?

A tier 3-5 tech that adds a small amount of HP 'Selective Genetic Augmentation' or something like that, so basically MRNA vaccination+Targeted edits for coagulation and reduced shock. Stuff that in theory could be done today but isn't tested, seems like a 'human' tech tree idea to me.