You can accomplish essentially the same thing with a little extra tagging and use of views. For example, you can create a tag that identifies the primary and secondary albums. Then you can have views of for primary, secondary and all. That would cut down the albums in each view. It would mean more views, but for the secondary albums, maybe you do not need that many views. And, you can use the hierarchy in the tree to hide the secondary ones most of the time. Or, you could also use the primary/secondary tag as the first or second level of the view scheme, which would mean not having to repeat the views for primary and secondary, although you would have to select it each time you go into a view.
Judiciously chosen views would probably make the library manageable - Early, Medieval, Baroque, Classical, Romantic, Modern, Opera, etc. Even Classical - First Viennese School if you have a lot of those. You can then use sub-genre or stacks to simply each view. For example, stack each composer and if you have a lot of one composer, further separate by some other criteria, like a range of years. There are multiple classical classification schemes that you could use.
The library is build for just this type of task. It is much easier to manage one library than two, as Dennis points out. I would experiment with various tagging and view schemes before separating the library into two.