SO_BINDANY in FreeBSD

[Mij]

Hello folks,

OpenBSD provides a SO_BINDANY socket option that allows an
application to produce traffic from an IP address which is not  
configured
on the host:

http://www.openbsd.org/cgi-bin/man.cgi?query=setsockopt

This is useful to run a transparent proxy which receives connections  
from
X and wants to connect to the real destination pretending to be X.

Is there any possibility to see this option implemented in FreeBSD? Do
you otherwise have workarounds for getting the same behavior with
reasonable complexity (eg, avoiding handling raw frames with bpf)?