Why are you looking to move away from your SonicWall solution? If you want the VPN tunnel to automatically re-establish or bring the tunnel back up when it drops, you can configure the firewall to use "Keep Alives".
With regards to users at the retail sites not being able to log in to their PCs without the DC available, it sounds like a problem with how you've set up the PCs. The PCs should have a local/cached profile saved on the said PC in the event the DC is not available. My corporate laptop operates this way as I am a remote worker and I don't have connectivity to my corporate DC until I log in and launch the SSL VPN client.
With regards to users at the retail sites not being able to log in to their PCs without the DC available, it sounds like a problem with how you've set up the PCs. The PCs should have a local/cached profile saved on the said PC in the event the DC is not available. My corporate laptop operates this way as I am a remote worker and I don't have connectivity to my corporate DC until I log in and launch the SSL VPN client.
