First of all ASA does not support multiple default routes (out different interfaces), so you can't do an active-active ISP setup. It also does not support PBR.
AFAIK, you cannot achieve stateful VPN failover in this manner. You could set 'two' crypto map peer statements on the other side, but this will not give you stateful failover.
Cisco recommends IOS routers for L2L setups, as they are more feature rich in this regard.
Regards
Farrukh