Think on a updated VPN Client:
The VPN Client initiates 2 IPSec/PPTP or SSTP Channels.
One to each ISP Link specified in TMGs ISP Redundancy configuration at the
same Time (or configured/random Primary/Backup) and uses the first Channel
coming up (Maybe with automatic reconnect).
I think this can be very useful to give a cheap high available VPN Solution
to Small and Medium Customers.
~egon