...what is the opinion of certain 3rd party activities like say, skydiving, bungee jumping, shark-cage diving etc...
After I get to the point where these activities evoke only the mildest sense of physical excitement, would I be able to relay this back to self defence situations?
Danger: adrenaline is addictive. This is a medical fact. The body's own endorphins behave just like morphine and other narcotics. You can build up a tolerance to its effects, but then, just like any other addiction, you'll start to crave more of it. When you stop getting a rush from one activity, you'll go looking for it elsewhere, which means you'll never reach a point where you get only a "mild sense of physical excitement" without deciding that the activity is now "boring".
And besides, learning how to handle yourself in a bungee-jump does not necessarily give you the tools to handle yourself in a fight. If anything, you might enter the fight looking for ways to get the adrenaline rush, and putting yourself in very dangerous situations.
Just my warning bell; I'm sure others can offer an alternative point of view on this, and I hope they do. I could be wrong.