Yes it could do. I think we need the prop to preserve old installations and introduce a new default in the future:
- WpadFqdn=no, today: to retain backward compatibility
- WpadFqdn=auto, future default for new installations: depends on accounts provider type
- WpadFqdn=yes, always use FQDN in WPAD file
We can reduce it to a boolean value though: case 2+3 could be collapsed together.