Very nice progress being made here. Been watching on and off since 2016/2017 and I'm glad this project is going to be released at some point in the (hopefully) near future.
City hall looks good but like said earlier, a North-Rhine-Westphalia flag, the city coat of arms and the German flag should be enough since we're assuming Ahlheim is located in the general region west of the "Ruhrpott" towards the border.
Kinda weird to then take the other state flags and planting them in front of the city hall.
One more thing, I plan on editing the Roadmap so it looks similar to what the BVG (Berliner Verkehrsbetriebe) and other places in Germany start to adapt, where the city street map is laid down and the lines are drawn into the roadmap, giving people a better idea of where they are and also because it looks nice 
I'll see how my progress goes on that and if it's okay I'd post it here when I'm done. No telling how long it'll take me and I'd have to browse through the thread in the Omsi Forum to get a general idea of where each stop is located since it's a bit hard to tell on the roadmap alone. 
Nonetheless, I wish happy building, planning and editing and I appreciate that the drive is still there to complete this monster project in your free time!
~Mucy
Edit: Anyone from the team, I'd need the original roadmap without the districts drawn in because I can't put the lines in otherwise without making kind of a mess. 