Twin PPP Setup (ppp-1 as ATM/DSL/PPPoE flag only)

Hi everyone, especially SpeedTouch owners,

I wish to know if someone has been able to use the
Thomson Speedtouch 5x6 "ppp ifadd" and "ppp rtadd"
CLI commands to access a pair of ppp accounts (one
from the main ISP and a 2nd acting as reference to
be used for confirming availability only). That's
possible on a viking-based device, as shown below:

http://img440.imageshack.us/img440/3206/doubelogin7vj.png

It might be nice to have InterNet access on one PC
thru an ISP via one sub-net while another PC would
be able to reach the Net using the other ISP via a
different sub-net but that's not necessary. All i
want to find out for now is if i'd have to wave my
double PPP configuration goodbye in a case where i
might come to replace the Globespan Virata bridge/
router with a Broadcom 63x8 product. A twin logIn
is usefull when PPP disconnections multiply, if my
ppp-0 interface is down while ppp-1 remains active
it means the ATM/DSL/PPPoE layers are operative or
ppp-1 would fail too. I wonder why so few persons
heard of it: