It isn't supported, because the 2 ISP with 2 different IP address isn't supported. If you want to create load balancing between two ASA, the requirements for it:
- The ASAs inside and outside interface must be in same subnet.
- the Isakmp must be enable on both interface, because the ASAs communicating each other with isakmp keepalive traffic.
But, you can't do it with two different ISP, which have 2 completely different IP address.
