I know that she can't acquire another mutant's powers by becoming them, but what about someone like Bruce Banner? He is not a mutant, and neither is the Hulk. Banner's "power" is practically an infection or a virus. So could Mystique become Banner, then get angry to become the Hulk? Using the version of her that can change her mass.
Or you can think about it like this: If Bruce Banner gets mad, and starts becoming the Hulk, at what point in the transformation would Mystique no longer be able to become the Hulk/Banner? Sometimes the transformation takes a while if he's fighting it.
Note: I don't see how this is duplicate to this question as I am ignoring that question by assuming that she can change mass and asking another question on top of it. If you read the old version of the post I had the same thing about using the version of her that can change mass, it was just not bold.