> The great thing about m0n0wall is: if you want some feature really bad and
> have a hard time waiting, you can just do it yourself.

Using a 5.X kernel with m0n0wall would be impossible. While you would have
to roll your own system from scratch, the web interface should be entirely
portable, or at the worst, require very minor changes. The startup scripts,
however, would probably require extensive review and modification though.