Include Network smb:// in Download Location possibilities - Vuze/Android
When picking a directory, other Android apps, e.g. ES File Explorer, LocalCast, offer navigation beyond just the local storage and microsd card. Other apps, e.g. Locus Map, allow the user to select a storage location using the "ES Save To" dialog through the Share interface.
Either way the result is the same - the user can select any storage location he/she has permission to use., including smb:// drives. Granted, this capability was severely restricted in KitKat 4.4.2, but it was restored in 5.0 and beyond.
Torrent clients work best when every torrent leached remains available in seeding mode until a reasonable ratio is reached. Restricting Vuze/Android to the available local storage on a mobile device makes it hard to be a good torrent netizen!