I am wondering if you have planed to support some IPv6 features of FreeBSD 
with M0n0wall. 

I think that the following features could be interesting:
  - regular IPv6 address on the interfaces and IPv6 autoconf (rtadvd support)
  - XinY ( IPv6 or IPv4 configured tunnel over IPv6 or IPv4 -> gif support)
  - 6to4 (stf)
  - IPv6 IPSec (supported by Racoon)

All of them are already supported by FreeBSD since the 4.x releases.

Regards,
  Vincent