If your car is outside of the permitted rules then you're disqualified, simple.
It's no different than running bigger brakes or using 6 wheels. If your car is out of the spec allowed you're chucked out.
Now how they prove it, and whether Mercedes would be stupid enough to try that trick? i'm not sure. Quite possibly a mechanical failure which if proved they should get away with it.
It will definitely be a huge moment in the championship. It would be hard enough to catch Max starting 6th, but any lower than that and he has no chance.