Sadly, I think the unique problem that is Duisburg will always be hard to cure, and many potential solutions that get implemented just have a knock on effect somewhere else.
My personal suggestion would be to change the traffic light timings on the central junction in Duisburg, as this area is the heart of the gridlock due to drivers coming out of the F7. Currently, these lights have a sequence as per the standard SCS base game cities, and therefore the green light duration can be quite short. A proposal here could be a similar timing sequence to the light outside of Duisburg that TMP added, which has a much longer green than any of the other lights in the standard base game. This could allow a large traffic to clear the F7 at one time, which would prevent people stacking up outside the entrance and blocking anyone trying to enter. The other idea could be the addition of a left filter light for the F7/tunnel sides, which could enable traffic from the F7 to head out of Duisburg on the peak route more easily. Of course, there will always be people that ignore the lights, which no one can do anything about.
My other idea is to implement what we call "box junctions" in the UK, essentially areas with a yellow hashed line, in which stopping on is illegal. If correctly obeyed, this would stop traffic getting boxed in and trapped on the central junction in Duisburg, which is the main cause of jams in the area. Perhaps if GMs are in the area, then a no nonsense rule of anyone stopping on such a junction without room to exit it being teleported could also be added? This could potentially be hard to police though, and could also provoke complaints being made against staff.
This system, if successful, could be expanded to other areas of the map, like junctions on the CD road, busier cites on Sim servers, or even up at Kirkenes on Promods. Awareness of these junctions and their meaning could be added to the TMP knowledge base, much like the recent "Smart Motorway" signs that were put on last year.
If the current idea of a total NCZ in Duisburg is maintained permanently, and once awareness of it spreads, then I feel that traffic will just head to the neighbouring cites of Düsseldorf and Köln instead, which are already reasonably busy. I also note that according to statistics, Amsterdam seems to have got busier this weekend too. This could be a coincidence, but also a sign that maybe people are starting to head elsewhere already....