Building Immunity: Fire

[Culture20]

Originally Posted by malloyd

Yes. These are inherent limitations that justify the low base price of Insubstantial, if you don't suffer them, you need to pay for them.

But this leads to absurd conclusions. If a character is insubstantial to unobtainium and only unobtainium, but doesn't have those two enhancements, he can't touch things made of non-unobtainium, but they can touch him. Worse: Insubstantial ( not insubstantial -100%), and suddenly you can't interact with anything because you have the insubstantial trait without the enhancements.
If the player wants to pick up or interact with things they're insubstantial to (unobtainium from above example), I could see requiring the enhancements.