Wow, quite a few answers came in here :D
We definitely don’t want to have a button for every roller shutter and I don’t see a problem with that. The switches will only be missing for windows that don’t have any importance anyway. Kids’ rooms, bedrooms, living rooms, offices, etc. will of course get switches. But for example in the hallway or in the bathrooms, where we have frosted glass, we don’t need anything. Even if something doesn’t work sometimes, which hopefully remains the exception, it’s not a big deal.
The Shelly 2 / 2.5 modules definitely seem like a pretty cool & simple solution that is also quite cheap. However, I have read multiple times that these parts get absurdly hot and even the manufacturer recommends using special cables that can handle up to 105 degrees. The standard, I think, is 70 degrees or something?! Honestly, I don’t have a good feeling about that and so these things are rather out for me.
We will probably go with Homematic IP now. They are available both as an [UP-modul], as well as a switch, and we can use our normal switch program with it. It’s a bit more expensive, but seems to me like a very well implemented and naturally enormously comprehensive option – please correct me if I’m wrong.