The Linux emulation isn't intended to be a complete replacement for native ABI. It's just a layer that upstream maintains in order to run a specific set of applications. This layer is severely limited in other areas and can't be used as a "general ABI for everything" as you envisioned (that is, unless you don't mind crippling Debian GNU/kFreeBSD and turn it into a toy OS).
If half the effort that has gone into the creation of Debian GNU/kFreeBSD went into improving the Linuxulator so that it could be used this way, would that still be the case?
Please try to found such (wo)man-power and we can compare later. Petr