kuchiku I just found this link http://openvpn.net/archive/openvpn-devel/2007-05/msg00004.html which allows you too Tunnel IP over ICMP and wondering if anyone has a mirror or a copy of the file posted since it is no longer available or if anyone has a similar modification for openvpn.
krzee good question! I posted a link to http://article.gmane.org/gmane.network.openvpn.devel/1983 in the dev channel (#openvpn-devel on freenode) im also moving this to the wishlist