I you do decide to go ahead and try a separate "Master" catalog, I'd first take the time to map out how you want the new catalog to look and how you might want to set up your file system (as in, if it was me, I'd have the Master and the Working catalogs on separate drives or at least in a separate folder structure). You could start by creating the new catalog, and creating the new master/parent folder within that catalog, then you could experiment with using the Import From Catalog function and also the Export To Catalog function from the working catalog. See how they behave, and decide what's right for you.
Be careful of doing any deleting from your working catalog until you are sure that things are working as you wish. You might want to try importing folders in their "current location" and then removing them from the working catalog, then going back to the master catalog and moving the folders into the Master folder. I'm just guessing here because I haven't done all this myself, but you can experiment and see what works for you.
I have two catalogs on my system, one with about 35,000 shots and another with my daughter's collection of a few thousand shots. The smaller one does run a bit faster (my system is a 2-3 year old duo core). I haven't tried moving things between the two -- I've just imported some separatly so the shots are in both catalogs -- let me know how it goes!