That wouldn't work, because only the first policy would be hit. What comes to my mind using a vpn group. I never tried it myself but as long as the cisco supports ike heart beat it should work I think. Normally You would use it to move the von from one location to another, with the same addresses. I think the backup is kept inactive so this is what i suggest:
configure two vpn's on the the HO side to the remote location. Both have the same remote gateway ofcourse (the public address of the cisco). Enable ike heartbeat on them. place both vpn's in a vpn group. Or use DPD as failover method.
A description of VPN groups is here (page 309 and furher) http://www.juniper.net/techpubs/software/screenos/screenos6.2.0/ce_v5.pdf
. Again: all theory, no guarantees (:-
I'm not sure you can configure the cisco to support this, same problem maybe, only the first VPN hits. Don't know enough about ios to advice you on this.
Please keep me posted, interesting problem!