How does one set up aliases per domain on a multi-domain site?
Domain Access does allow you to have per-domain auto alias settings (but I have never tried this), but I am only seeing one alias on an edit page.

A less than idea option if you are using Panels is to have a panel page for each path, and then create a selection rule for each domain, and then assign the node that way.  This would be a lot more work, though.