I see many different plugins here, and I'm fairly certain that everything I need can indeed be done, but I'm not quite sure how (and which plugins to include). This is what I need:
1. WordPress MultiSite Network in which a master store houses a master catalog (or rather a set of catalogs, each containing many products). By "catalog", I'm simply referring to a grouping of products - I understand that you may not necessarily call a collection of products "catalog"...
2. Admin can add new sites to the network at will, map each to a unique domain, AND automatically enable catalogs of his choosing on the new site. This may include some of his catalogs, or all, and could be different for every new site.
3. Admin can change prices on any catalog on his core site (as in applying a sale or promotion), and these prices are automatically reflected on all other sites that feature said catalogs.
4. Here's tricky piece number 1 (at least, I think this is the first tricky piece): Orders placed from any of these catalogs from ANY site in the network, get submitted to the same single CORE site (while retaining information about which sub-site sent the order). Ideally, this should be done by enabling the entire sale process to complete within the user experience offered by each sub-site, but a decent fallback would be to refer all orders from all sites to a single order submission page that is common to the entire WordPress MultiSite network.
5. One more tricky piece: The products number in the THOUSANDS! They come in via CSV, and need to be injected into the system repeatedly, such that existing products (after the first injection) are updated and never simply duplicated.
6. Owners of sub-sites can also add their own products to their own catalogs (can be separate collections or catalogs or different areas of the sub-site with any other name), and set their own prices for these items, but they CANNOT change the prices from the core catalogs (those inherited or imported or injected from the main core site).
7. Owners of sub-sites can choose their own themes from a collection enabled by the network admin.
I imagine all of this and more can be done with existing WPMUDev plugins, but I'm having a tough time determining which to select (though number 7 seems fairly obvious)... Can you assist?