I agree, but the problem was that there was/is very little to differentiate radiation poisoning from, say, a parasite if you happened to miss some of the prompts or just aren’t familiar with them. I suppose the easiest way is a geiger counter, but if you don’t have one or don’t realise you need one, that can be a problem. It’s easy to just forget that radiation exists and get really confused, even though your character has level 8 first aid and should probably have some idea of what’s going on. Then again, at that point you probably have half a dozen geiger counters…
I like all of your ideas, especially the dead animals around wilderness hotspots. I know I’ve had at least one occasion where I wandered into an area (I think it was a helicopter crash site) and randomly picked up 800 rads or so. It really didn’t strike me as somewhere that would have radiation…
I also really like the self-diagnosis part, even if it doesn’t include radiation poisoning. I dislike the idea of “oh no I’m puking for no obvious reason” followed by the player downing random medicines until it stops. That just smells of bad gameplay to me.