This sounds good to me.  Indeed, using locking amongst multiple chroot
jails seems just a bit redundant. I've never had any problems with
read-only null mounts. ;)

I also don't think the added dependency is a worry; no one seemed to
have a problem with pkgtools/shlock being a dependency ...

Could you make this tool available at a URL and/or commit it
somewhere?  I'd like to start using it.

--Blair