Libraries are also tied to a lot of settings in Media Center, as such its a really risky undertaking to load another one and then hope its still configured to respond to the same remote configuration. I don't think we really plan to do anything here.
But as the others have said already, the library in Media Center is extremely flexible, you can do any sort of audio categorizing in any way you want, keep different tracks entirely differently arranged, categorized by quality, source, or whatever. Genre is not the only field we have, and you can even make your own to organize files in any matter anyone could imagine, and adjust the views both in MC itself and for JRemote to reflect any sort of organization you want. There is no practical reason for multiple libraries to exist just for the sake of organizational properties.