Going to larger (more positive) is especially precarious, because it places the back of the wheel further in board, running the risk of rubbing suspension components etc.
Going smaller (more negative) pushes the wheel and rim away from suspension, and possibly out of the plane of the wheel well. That may be OK functionally, so long as the fender doesn’t hit the wheel (including under full upward travel). Looks wise, people probably have mixed feelings, but these are just winter tires you are talking about...
Here is a snippet of an article on the Internet:
This is why that ideally, you don’t want the new offset to be more than 5 millimeters away from the old offset in either direction. However, this isn’t always possible. What you do need to keep in mind is that more negative offset, i.e., an offset that is less than the original, will push the wheel out farther from the wheel well. Usually, this will not cause a problem, although it might result in a pretty funky look.
In contrast, too much positive offset is a danger, as it will push the wheel farther in toward the suspension. Here’s an extreme example: If you have to go from a 45 mm offset to a 20 mm, the wheels will protrude from the sides of the car. But going from a 20 mm to a 45 mm offset not only may destroy the tires, but also has the potential of affecting vehicle control and injuring the customer — not an optimal customer service outcome!
