I have read this thread from start to finish as well and I'm shocked. Come on Mediamonkeys, where is the freaking multiple library support??? It's been five years that people are requesting this. I landed here after searching Google for the same thing. When I typed "Mediamonkey mu" right away there were two matches in Google's list of suggestions: mediamonkey multiple libraries and mediamonkey multiple databases. "Well okay," I think, "many people are obviously looking for it, so it must be there. Probably just an option hidden inside some menu," I tell myself...
So imagine my utter dismay when reading this thread and finding out that after fiiiive long yeeeears of people searching and requesting ...it still doesn't exist.
I assume multiple library support was never given any thought during the development of this otherwise great program, but it is an elemental feature of any sophisticated application that deals with data manipulation. Implementing it at this late stage probably requires a lot of file and database restructuring plus code rewriting, but if you want to play with the big boys you're eventually going to have to bite the bullet. If you don't, it will be the main reason why MM never got rid of its amateur status down the road.
A large part of MM users are tech savvy people who obviously want this functionality and they are sick and tired of resorting to clumsy, ugly hacks. Aside from not wanting the dumb wife or teenage kid mess with their carefully crafted music files, or the need to quickly test scripts and what not against a copy of their own stuff instead of risking corruption of the real database, there are dozens of other valid reasons people want truly separate databases. Perhaps get some ideas the way Firefox uses profiles, each with its own folder and settings. Things like that. Do some brainstorming and in six months from now this stuff is over and done with. And while you're at it do some other things to make this finally an all-in-one music manager, like improve on Dimitrijevic's already great RegExp Find and Replace and build it directly into MM, with support for action groups so people don't have to use third party music file taggers.
Of course I'm not holding my breath. Going by the way most things on the wishlist are treated it will always be just that; a wish.