I would love to see a feature added like Cisco Anyconnect where if a users AD password is set to expire or expiring soon, that the VPN client will process the password change.
The following feature requests are already in place, depending on how you've set up SSLVPN authentication:
FBX-3898 Change RADIUS password via Mobile VPN w/SSL (if via NPS or a 2 factor auth system.)
FBX-1797 Change Active Directory password via Firebox AD authentication (including SSLVPN)
If you'd like to follow either, please open a support case and mention the FBX number, the technician can set notifications up for you via that case.
WatchGuard Customer Support