I think you are on the right path. I think we should just do away with flagging posts altogether. It seems to be the most abused action on here and there is a reason that FB did not include a dislike button.
Like you I think we should be able to flag users for very limited reasons like fraud (which is what plagiarism is in essence), spam, etc. but no "muh feels". If you see spam or plagiarism you flag the user and check the appropriate box then maybe a witness or 3 or 9 witnesses check the flag. If the flag is appropriate, then the user gets a mark. If the flag is not appropriate then the flaggot gets their rep taken down a notch.
Reputations then will be based on upvotes, followers, and engagement and we wouldn't have to worry about our posts being negatively impacted by someone with a grudge or is just being a jerk or holier than thou.

I appreciate you taking the time to bring this to our attention.