Not a DLC suggestion, obviously; but a structural suggestion for TS 2022 maybe. Why not make it possible, automatically or via the editor, to link up owned routes that include the same places? For just one example, it would be possible using existing DLC to run Augsburg - Munich - Garmisch - Innsbruck.
Someone on the Steam Workshop already does this, they've done multiple routes already. https://steamcommunity.com/workshop/filedetails/?id=341255096 And here's what you actually suggested as a merged route: https://steamcommunity.com/sharedfiles/filedetails/?id=1099706245
Okay, that's pretty much what I had in mind-- but rather than something which can be done only by veteran route developers, rather a tool in the game editor itself which allows any slob (like me) to plug Route A and Route B together so long as they share a portal.
Good in principle, problem in reality is that routes don't always join up on the in game map, and there are even different versions of the same route in game where station co-ords are on different elevations, so it can take a veteran route developer to sort that mess out and make it all join up properly
