rndmE Could it make sense to just build an empty WebView-App which contains maps.google.com?
You might want to try this
what is Google Maps able to communicate to other apps? Can they communicate as they want and it just depends on the developers of these apps what they share?
Google Maps is able to communicate with another app what itself and that other app have both been programmed to share. Inter app communication works on a mutual consent basis.
Can they communicate as they want and it just depends on the developers of these apps what they share?
So as I said, in theory yes.
I would maybe be fine with having Google Maps installed in my device if I'd be sure that it would not tunnel traffic or gather data from my other two Google apps.
No way to be sure of that at the moment. That doesn't mean it happens; I personally think it is unlikely that Google uses inter-app communication to circumvent such uncommon and marginal roadblocks to data collection.
What else does Maps communicate to the Google servers that I may not have on my screen besides the data that is necessary for using Maps?
Again, no way to know.
Are there thoughts from the GOS team about features like denying communication between chosen apps
This feature is planned, although no ETA.