Tom
It can be done and it is quite simple on the ASA. The solution does not involve multiple tunnels on the ASA and does not involve roué deletion. You would simply modify the configuration of the ASA tunnel to specify a second peer address. If your config looked something like this
crypto map vpn_map 10 set peer a.b.c.d
you would modify it to be
crypto map vpn_map 10 a.b.c.d e.f.g.h
With this configuration your ASA would negotiate the VPN tunnel with a.b.c.d and if that peer became unavailable then your ASA would negotiate the VPN with e.f.g.h. Note that failover here is automatic but that it does not automatically fail back.
HTH
Rick
HTH
Rick