Yes, streaming is in focus. The big streaming platforms solved features like "radio" really good, but what these services not providing is an advanced music organisation, which is the domain of MM – and they wont provide it the near future, cause their application are design to be simple.

I agree with this, and there are commercial reasons to consider it as the momentum swings the way of streaming services (especially in light of recent events with Google). Might also now consider making a real effort with Linux too as Ubuntu phone launches tomorrow.

OK, then there are no main technical problem to implement a streaming service. I'm able to create such a script, but I do not have the time and passion, and I don't like a isle solution without benefit for others.

Isnt't there a way to cooporate with a streaming provider? Just start with one to show that it works and it's makes profit – my favorite would be Qobuz They could then provide a dll plugin which respects their API rules.

there has been some trouble with accessing some online database's with mediamonkey or its addon scripts one database owner threatened legal action if it wasn't stopped. they get touchy about scanning their stuff unless you are on their site.
so might not be a good idea to gather all the info in all the databases with one program.

Umm? at least not where you could publish it online. you might make the script yourself and keep it on your system for you only.
that might make it through all the legal hoops ?

Having all music in one application would be great! Players for streaming services like Spotify, WIMP, Amazon Cloud, Qobuz and others are all different and have limitations in their usages.

Cause of all these streaming APIs are different – I know no industry standard (used) – such an API could provide an easy way to map these data to the MM library, e.g. by a plugin script, to configure how to access authentication, metadata, playlists, search and the streamed content.

Would this need much additons and modifications to handle streamed data, to write custom tags or to save offline content?