Maybe add different levels of splints, lower first aid, is a makeshift splint, chance of not holding long enough so needs to be reapplied, takes longer, higher skill makes a more effective one.
Finding a vein isn’t that hard for most people, if it was the druggies out there would have to go to medical school to shoot up. Not sure how if you missed the vein a mutagen would give you bad mutations, maybe not work properly so lower the chance for the mutation to happen, add more pain then it already causes, but that would lower the chance for good or bad mutations. Guess you could add in a line of partial mutations, only the arm/leg or where you injected it gets a chance to be affected, but that seems like a lot of work to only apply to starting characters, after all it only takes first aid 3 to make a serum.
As already stated, inhalers and oxygen tanks are not hard to use, you breath. But I have seen people not be able how to figure out a lot of things that seem simple, like pumping gas, or using an ATM, so maybe if they have a really low INT. they could fail, get a message, “You can’t figure out how this works, maybe it goes in the other end.”
Course there are some who think INT level should cap how high some of your skills can go, makes sense to me, some people just can’t grasp more complex things, no matter how hard/many times they read the books
