Nicely cherrypicked scriptures. There is a danger in applying 1 scripture literally without a proper context.
Remember Pauls letters are written to the congregations - not elders only. He was warning people to watch out who they associate with - no shunning is defined here in the deformed way it is practised in the JW faith.
1 Cor 5 - in the very next book Paul says to welcome him back in. Again in no way supports how we handle cases like these and how we treat "sinners".
2 John - is talking about the anti-christ not other sins. Of course we would not want to associate with them, but we can still treat another human with dignity. Again no judicial process is here mentioned.
2 Thess 3 - yes it is obvious that if a friend gets drunk and starts smashing your house you would remove him right? Same applies here - but notice vs 15 - And yet do not consider him an enemy, but continue admonishing him as a brother - hmmm - can't see shunning here either?
Rom 16 - yes if you had a group of any sort meet at your house and you had a person causing troubles and divisions you would avoid them also. But avoiding is not shunning. No elders are involved, no committees, etc.
So far I cannot see proper scriptural support for the way JW's handle committee cases.
I understand the need to watch out for people who could influence you but that applies to our general daily lives. You could apply that to a circle of friends.