I regulary generate lists of pages with PetScan and other tools that can work PagePiles. When I need this list for AWB I have to make a PagePile, then export it as "Plain text" then save it somewhere locally and open via the "Soruce: Text file (UTF-8)" feature. It will be much easier if AWB can open provided PagePile URL as and load the pages list.
Yes, the UI could require just the PagePile ID and the data could be received in a various ways. The PagePile support feature could also export the current AWB list to PagePile for additional external processing or for sharing with other AWB users.