With the big succes that The Niddertalbahn had, I wanna suggest a morden version of it, that would expand it to Frankfurt main. Now I couldn’t find any information on how many miles it was. So if anyone can provide me that, I be happy. But the route (RB 34) that goes from Glauburg-Stockheim to Frankfurt Hbf takes around 1 hour and 14 minutes. So basically it’s two additional stations in the expansion, that will be Frankfurt West and Frankfurt Hpf. I heard about Matt talking about the size of Frankfurt Hbf. So obviously I don’t know if this is realistic. But if it was, I think this route could be a big success.
What you're proposing is merging Niddertalbahn with the PC editor route Main Weser Bahn at Bad Villbel with RB34 fast to Bad Villbel from Frankfurt Hbf
Maybe you didn't notice it, but this is already happening as the most advanced community route project so far, die Main-Weser-Bahn from Friedberg to Frankfurt Hbf: https://forums.dovetailgames.com/threads/main-weser-bahn-frankfurt-friedberg.75795/ Either pilot21 will share if for free or he could team up with DTG to officially release it, when it's ready. It will not be an extension to Niddertalbahn though, as rather a standalone route.