I would love to see Spotify as a plugin for MediaMonkey. MediaMonkey is my favourite music player, because of its really complex library system. This is what I love about it.
I find Spotify and even Premium, being a very stripped and simple music player, which of course can be convenient mostly, but sometimes just lacks functionality. I could give a lot of examples, but lets leave it out. See, there is also some functions like, Related Artists, and Radio, which are just genious, and I would love those features to be accessible in MediaMonkey.
In a practical sense, I think that what has to be done, is that the Spotify-plugin should be downloaded from this page as an addon:
Spotify-team could either make it yourselves or give it out to developers to do it.
Another twist to it, could be that Spotify-team contacted MediaMonkey-team so that those two teams in cooperation could develop a new MediaMonkey-version with Spotify incorporated in it. That way, Spotify would gain an even bigger target audience!
Please bear in mind that the Community is not an official Spotify support service. It's a place where we all help each other, whether we work for Spotify or not. So please use your discretion when using the forum.