I think the idea of the Berlin S-bahn to be in TSW 3 is a pretty awesome idea. It wouldn't matter what service it would be. The crucial thing to be in the Route would be the BR 481 and the BR 483/484. It's a pretty requested route and would have amazing views of the Capital of Germany.
Excellent idea but there is going to be a problem with the train protection system is that it uses Zugsbeeinflussung S-bahn Berlin & fahrsperre leading players to treat it like PZB yellow signal reduce speed to 85 kmh then drop to 25-50 kmh. Very different from third rail PZB Hamburg S-Bahn Hamburg Verkehrsverbund (HVV) since it can be played like a Normal German and Austrian Österreich Bundesbahn routes that are PZB only.
I have another idea to this, it would be cool if we get the 481 501, 502 or 503, as those are the only 481s that have 4 cars in one unit, with carriage crossings inbetween, unlike the other ones which are only 2 cars long see here:
