I believe it's impossible to squeeze relatively recent (9 or 10) FreeBSD versions down to that size. The linked git repo makes mention of needing at least 8MB for some builds. And you don't get IPv6 at that size.
It could be fun to take something like the BSD kernel and an alternative BSD licenced userland to make a much smaller footprint device, but I don't have the energy to /also/ do that.
If someone would like to do that then please do step up and do it! I wouldn't even mind if the FreeBSD wifi stack and Atheros MIPS support was ported back to NetBSD and NetBSD was used for this purpose.
Anyway, it was a good read, thanks.
I'll have to get on freebsd-mips and start getting annoying with my simpleton questions :)