I think it's all worked out. I encountered a few problems where it was accessing the wrong database (the cross-database VW3 importer wasn't choosing a unique database identifier for the source connection, while the other importers were already doing this as designed).
However, I was not able to get all the way through the import process due to a 503 service unavailable error. I'm not sure if maybe I tried to run it while a database was backing up, or if there was some more verbose message I didn't have access to see. Please let me know. Otherwise, I'm leaving this marked resolved.