If magic causes unicorns then when we take unicorns out of their magical environment they will perish or stop being unicorns. If unicorns cause magic then the unicorns will be fine if we take them out of their magical environment then they will spread that environment to wherever we put them.
I understand what you oppose of my idea, but I see this as the essential part, so I will try to give you a different vision to yours. Then you can really dislike it

My point regarding this (the feedback loop), is that I appreciate Magic being more complex and subtle and mysterious than anything else, i.e. not only a property of a place that changes what spawns in a certain area, or the special abilities of a certain creature. I like the idea that Magic is something delicate and pervasive and volatile and powerful and weird and incomprehensible.
(As much as possible, I'd like Dwarf Fortress to embrace something that takes less inspiration from D&D/World of Warcraft and more from medieval textbooks, books of fairytales, and the shivers you get when you walk at night in a cemetery....here's my secret mission
)Therefore I like the idea that anything that can express Magic, is also a vehicle of Magic, not only a device to exploit some of its properties. I understand if you see it as highly impractical or hard to design or implement or whatever...but do you get my point?
Lava is cool, and dangerous, but if you know how to manipulate it, there's few to no risk, and no surprises especially. Magic, on the other end, should never be safe, or 100% predictable. The most powerful mages can deal with the most powerful Magic, but are not more safe from its danger than the inexperienced mage, but in a way it's totally the opposite as the danger is intrinsic to Magic, and more powerful spell mean...more FUN! If Magic is something you can manipulate and turn to your will, than it's not "magic" anymore, it's just another cool gadget, it's technology.
That magical artifact, the more powerful its magic, the more it should twist the reality around it. If a creature picks a powerful magical ring, and carries it around for a long time, he'll eventually acquire magical properties
(does this ring a bell?). And all the same, a sword left in a pond in a very magical lake, might become magical.
Maybe this doesn't answer surgically to your point, but I think it does in a certain way. If it doesn't, I'll try to be more precise with our next exchange