Hi Torsten,
I don't know how MNE is popular since I'm not a dealer, but from time to time Marklin produced some very local articles - Tegernsee Bahn, Allgäu-Express, 2 Metronom trains. So, for me, MNE or IRE Berlin-Hamburg at least have a right to exist in Z
And MNE is not a subject of high priority for me (ICE4 or ICE2 would be much better, but it sounds totally fantastic). All in all I think that wide assortment is a sign of the good health of this or that model train scale.
As for Touristik train sets, my personal opinion is that two almost identical trains were just too much (at least for such a short period). Furthermore, they have been sold at the same time (or close to) with two Lufthansa Express trains that had special features like interior details and lighting. Of course I understand that these features aren't critical for many users, but for me it's like that.
Greetings,
Alex