Now two proper questions: First, do you think the opinion of the Emperor and the other rulers would forcefully overrule another realm if they felt it was dangerous to the empire was a whole?
Depends on
how dangerous, but yes, I would think the Emperor could and would.
Second, when you talk about how external wars would be thought, do you mean to say you'd rather everyone do their own thing or do you think that the rest of the Empire will usually (say with a smaller realm of the Empire declaring war on a larger external foe) to avoid being weakened as a whole?
Individual. If a tiny realm of the Empire starts a fight it can't win, then it'll lose. Jenred's not interested in saving idiots from themselves.