I really like the idea that Riesa-Dresden will include ICE services (for everyone, as everyone has SKA). My suggestion would be to do the same with Hamburg-Lübeck. Hamburg and Lübeck are stops on the ICE line 25 to Munich and, like the IC, see a few connections per day. So the ICE should fit into the timetable here and would add to the variety of the game.
Speaking of ICE Line 25 it runs on Hauptstrecke München-Augsburg therefore it must get DB BR403 ICE3 or Schnellfahrstrecke Nürnberg-München DB BR412 ICE 4
That is correct, but not everyone owns HMA and the 403. If you do, then of course the 403 would be better. On Riesa-Dresden, they are using the 406 where in reality the ICE-T are running. Hence my suggestion...