I don't know if this is the same thing as multiple instances of Moving Pictures. But my suggestion (if possible) would be to be able to have multiple "shortcuts" on the home menu. And be able to configure thoose shortcuts with custom names (like now) and custom filtering.
For example I would like to have one shortcut for "Movies" and one called "Concerts". The shortcut "Movies" should load Moving Pictures but filter out everything tagged with genre "Concerts". And the shortcut "Concerts" should load Moving Pictures but filter out everything everything except thoose tagged with "Concerts".
I understand multiple instances of Moving Pictures is not the same thing as filtering, I was just saying that in your situations they both solve similar problems. Again though, there are a lot of hurdles that make implementing official support of multiple installs very difficult.
Ultimately though, the setup you are describing is also outside the scope of Moving Pictures. Moving Pictures is designed exclusively for movie content. If you want to use it for other things (like for concerts for example) that is great and I am glad you are finding new uses for the plug-in, but that is unfortunately not an area where we are focusing our efforts right now. See this thread for more details.
Just want to give my two cents. I understand that multiple instances of the same plugin is difficult, but what about Johan's suggestion to have a direct link to a certain filter at the home screen? You could have one database, one plugin and for the people who want to use this plugin also for concerts (I am one of them), you could just make a shortcut to this filter on the home screen. I for one would very much appreciate such an option, because I don't feel concerts belong in the movie section. Moving Pictures is such a great plugin though, that it would be nice to have it monitoring my concerts as well. If this would give a lot of problems as well, I totally understand. I will look for a different solution then.