I watched some trainspoting videos at Hamburg HBF on Youtube and the Dostos have the doors above the bogies
Ah, got it. Those are Bombardier TWINDEXX Dostos. Most of them are owned by DBFV and run as IC2s in white paint; a few are owned by DB Regio but the only ones in Hamburg run to Kiel and Flensburg, not Lubeck.
Running the 112 (fast 143) on RSN would be highly unrealistic. DB put the poky 143s on passenger service there because the line speed never goes above 120. And it would in general be unrealistic to run Gen 5 Dostos in red Regio paint on any of TSW's existing routes, since they aren't to be found there.
As you said, the route will probably not include gen 5 dostos, but chances are we will get an improved version of the current Dostos, which are starting to show their age. I hope these new DoStos (not the Gen5) will replace the old ones, DTG already showed they don't care whether or not the destination displays work. The 112 would not run on RSN, but on all the other german routes where the 112 can run IRL, since I'm guessing it will be ready before many of the fixes to the BR146, which right now is about acceptable in terms of sounds, and is not on par with many of the recent additions to TSW2.
I looked at some photos from hamburg lubeck for train simulator and it uses the coaches that I spoke about
Actually, these aren't TWINDEXX coaches but just regular Dostos (3rd gen I think, see the destination display). All TWINDEXX coaches in Hamburg have the Schleswig-Holstein-livery (blue/green), and are run with 445s at front and back. All generations except 1st gens also have variations with doors over the bogeys.
I think that the destination display will show the correct destinations because the Dostos will come with the route
There would be a case for people to say: I would rather have the old DoStos on the older routes even if Hamburg-Lübeck comes with a better version of the same DoStos because the old ones will have the correct destination for RT, MSB and RSN and half RRO. To the possibility of this criticism I wrote earlier that this system of display destination is ""no longer supported"" (albeit with awful wording "DTG doesn't care" wasn't really the best way I could describe what I meant... sorry) as the game is moving towards a system that will place the correct destination on the train, instead of having to memorize all the possible destination on the MSB DoStos for example. So a system that is route dependent instead of train dependent, so I was trying to say that, IF we get new DoStos they should replace the older ones even if they are missing the destination for older DLCs, as that will get fixed with time, and the current DoStos lack a lot of destinations already.
Bringing low-entry Dostos with Hamburg - Luebeck would be totally unrealistic, since they were never used on that route. In fact, most Dostos in former West Germany have high entries over the bogies, the first ones being the Schindler Dostos (derived from the Re450 Zurich S-Bahn push-pull trains, which have high entries too). So especially on SKA, HRR, RRO and HMA the low-entry Dostos were in fact never used there. On RSN, Dostos were never used anyway (apart from the 143 + 1 cab car trains on RB 56), but even if they were, if would have been high-entry Dostos, since the standard platform height in North Rhine-Westphalia is 76cm, while the low-entry ones are built for 55cm platform height, which is the standard height in the former Eastern part, but also a few regions in the west (Rhineland-Palatinate for example). The cab cars always have their doors on the lower level, the 3rd gen onwards has automatic ramps which can be used for 76cm platforms, the 2nd gen has a version with the doors on 76cm height and built-in ramps inside (DBbzfa 761.2). The 112 was used on RRO for the RE 7 services a few years ago, it was used rarely on RE 4 services, too. The attached picture shows a 112 with high-entry Dostos on a RE 7 service at Wuppertal Hbf (photo made by myself)