I have posted to the ipsec-devel list and haven't gotten any responses. Also I have spent 2 days googling with no results about the above setup. Is it even possible to tunnel ipv4 packet thru an ipv6 ipsec tunnel?
AFAIK, No.
IPv4 & IPv6 are different protocols so if you want to move IPv6 traffic over a IPv4 IPSEC tunnel you need to encapsulate the IPv6 payload within IPv4 packets. The reverse is also true of IPv4 over IPv6.
This is why tunnel brokers like Freenet6 & Teredo exist, you can't push IPv6 traffic out across an IPv4 only network without tunneling.