Thanks for your reply.
You're going to physically move the images? If so, unless you move them with PM, the catalog will lose track of them. C1 Sessions can't reference images wherever they already exist?
I'll move them using only PM+. I know they'll lose their links to the PM database if I do it otherwise. C1's sessions, unlike catalogues, don't contain referenced-only images. (They were designed originally for tethered shooting, typically by studio photographers doing, say, a catalogue shoot or perhaps someone doing senior photos—that kind of assignment.)
Sessions contain the image files and their sidecars—and the entire collection of C1 edits in separate XML files. This scheme makes a session easily portable. If you need to transfer a session somewhere, you just move its entire directory tree. There's no database to update. It's a workflow with advantages for some people, while others prefer C1 catalogues. I have always preferred the Session workflow. A common approach at, say, the end of a year is to import the year's sessions into a single catalogue—at which point the images
are located only by reference within the catalogue.
No reason to create collections for this purpose that I can see. I suggest starting off small and make sure your entire workflow is worked out before committing to any one particular method.
That'd be great. If the filtering alone can do the initial organizing job, so much the better. Thanks again.