There already is a way to turn off all of the HFS, it's turning off the lower layers in worldgen. Granted, that's not the topic of the whole thread, which is just limiting HFS access, but it's not like it doesn't exist.
I also generally choose not to mine the candy most of the time, at least, not until I'm "ready for it", as an instinctual habit from the 40d days when it brought the monarch early and could screw up your fortress progression. Even now, what little "difficulty ramp up" exists in DF occurs based upon fortress value - the more value in materials in your fort, the more frequent FB attacks become and more powerful sieges are, to the limits of the game's ability to actually muster those kinds of attacks, which are, granted, declining more and more as the game's simulationism trumps its gameyness.
In Gnomoria, which is very much a more gamey version of DF, sieges are directly proportional to total created wealth, which means that it's a critical gameplay strategy to limit access to iron and steel until you have a powerful, elite military, because steel items are 25 times more valuable than mere bronze, and it means that you face sieges from enemy forces with a dozen elite goblins wearing steel with ettin backup rather than half a dozen goblins with maybe some copper armor on a few body parts and some wooden hammers.
To that end, I don't touch the bluemetal until I feel my fortress has matured enough to actually use it properly, which starts with having a reserve of elite fighters and legendary smiths who can actually use the limited quantities of the stuff to ensure as many masterworks as possible.
As for aquifers, there are ways to remove those, as well. In fact, it's such a popular thing to do that the Lazy Newb Pack outright makes it as simple as a button press on the front page of its launcher.
People who "refuse to play with aquifers" don't find the settlable world cut in half, they just turn off aquifers, and can settle the whole world again.