I don't speak german so Ill respond in english 
But I got started with a youtube video of the Netherlands 3.0 beta mod and that was also the first mod I ever played and I remember it having the script that you could dispatch riot units in front/behind the vehicle and they would line up and I always loved that so much haha.
What I do miss are maybe some more english EM4 tutorials, I know steenkolenduits so going by and reading this forum kind of works but thats also where it ends for me haha. I like tinkering around with scripts but anything like modelling or stuff I have no clue how that works. (Coding is my job so thats a whole lot easier haha).
Functionallity wise I would think it is cool to get some more police involvement. Think of like questioning witnesses, at big events forcing an area to be evacuated (I think this is already in FUMB with the WWII callout) or a car vrash investigation like in ERS Berlin.
Setting wise something way more industry foccused (like e.g. Tagebau) or for example a harbor fire brigade (e.g. The dutch marine has a specialized fire brigade for the Navy, which would combine the military / navy and industry together which is not something that happens in a lot of mods). But honestly I think it is already great mods are even being made so (Even though outside scripting(/coding) I can't do anything submodding wise lol)