I will list for every route Loco-DLCs which would make sense on this route. Rapid Transit: BR 143 with DR-Dostos Ruhr-Sieg Nord: BR 143 with n-Wagen for the RE16 and RB91 (Substitution) Main-Spessart-Bahn: BR 151 for the Spessartrampe BR 642 or/and BR 628 for the RB Aschaffenburg -> Miltenberg BR 111 with Moduswagen for the RE54/55 Rhein-Ruhr Osten: BR 111 with Dostos 3rd Generation for the RE4 BR 143 with x-Wagen to fill the gaps in the timetable from the S8 (every 4 houres, 2 trains are missing and the trains to Wuppertal-Oberbarmen are missing) BR 1440 for the S8 (other timetable or to fill the gaps from the S8 (just descripted above)) Hauptstrecke Rhein-Ruhr: BR 1428 (Flirt 3) for the RE42 BR 143 with x-Wagen for the S1 (Essen - Dortmund), the S6 and the S9 (both AI) More ICE trains Schnellfahrstrecke Köln-Aachen: BR 643.2 for the RB20 Hauptstrecke München-Augsburg: BR 440 for the regional trains Munich to Augsburg BR 111 with Dostos 4th Generation (but built in 1997 and not around 2003 - 2007) More ICE trains Of course they also are a lot freight trains that would fit on all of these routes, but I don't listened them now.
This would be my favourite out of your suggestions. MSB could really use a Br 151 DLC to be a proper farewell to the real MSB.