I understand that Debian GNU/kFreeBSD currently builds software using the FreeBSD ABI. It might be easier to make some changes to FreeBSD's linux emulation and Debian Linux's packages so that the FreeBSD kernel could boot a Linux userland using the same binaries used in Debian Linux. This would make many things start working and reduce the things that you need to maintain dramatically.
Please could, you give us some examples of what does not work correctly using FreeBSD ABI and works using Linuxator ABI ?
There is not much interest in this in either Gentoo or FreeBSD, but I thought it might be worthwhile to share the idea with you. Right now, I have Gentoo Linux's userland running in a FreeBSD jail nearly perfectly, so it is definitely possible.
What kind of userland ? Do you have working X-server, attached printers, cameras, ...
Please see in http://wiki.debian.org/Debian_GNU/kFreeBSD_FAQ Q: Is it possible to run Linux binaries under Debian GNU/kFreeBSD kernel?A: Only as long as standard FreeBSD Linux Compatibility Layer is sufficient. Some symlinks might be missing. The basic linux-i386 chroot of etch and lenny under kfreebsd-amd64 and kfreebsd-i386 works.
... Petr