I believe there is a way to do it dynamically and allow the user to choose which players they want to allow access to, and then accept the changed permissions. However a majority of my user base will not care, and would actually prefer the one click install ease of use. At least that's my reasoning.
For those of you really concerned, you can download the source and modify manifest.json to change where the contentscript is injected for peace of mind. https://github.com/kkamperschroer/Musicality
I'll continue to look into ways I can deal with this without blindly asking for everything. I haven't found a good solution yet, but that doesn't mean there isn't a better way to do it out there.
I'll work on refining the title and description. It's really a quick-and-easy controller for online music players.
Thanks. :)