Heres a few survival'ish ideas:
-Make it so you cannot go to doctors to cure addictions. Increase the power of all chems and alcohol to make them a more attractive choice to take on enemies, but also make addictions easier to succumb to and withdrawal a real problem. Maybe also scale the withdrawal according to which phase you are in (mild starts, severe cravings, starting to finally come off (back to mild)). Finally make it so that the only way to come off a chem is to either visit a certain vault (ideally include an expensive raw materials cost) or by stopping its use.
-Re-introduce Radiation sickness. By accruing a certain amount of radiation (irregardless of removing rads) you develop sicknesses that last a few in game weeks. The sickness could be a basic reduction in your SPECIAL, and every time you accrue a balanced amount all your SPECIALS will lose a further one point.
-Re-introduce diseases from animals (outside of Vault animals) so that bites give you disease. Use a base of ten to trigger the diseases and their severity, e.g. 10 molerat bites = molerat disease, 100 = severe molerat disease, 1000 = super-severe, etc. Make it so you cannot cure diseases unless visiting a doctor to remove EACH disease for a hefty price (for example each disease would cost 1000 caps).
-Make tobacco a useable item, and do something similair with the above chems idea. Make it worthwhile (maybe each cig replenishes your critical bar? But cannot contribute to Critical bank), but make the withdrawal a real issue to deal with.