what about following the fsstnd...
or the fhs as it is called now. It describes how everything should be laid out. It is primarily aimed at Linux, but is supposed to be ably to be used by any Unix, or Unix-like OS. I think that at least getting all (or at least most) of the Linux distros to follow this would be a great help.
I do realize that you are talking about a Unix-wide source package, and obviously we could never hope that all makers of Unix could switch over to using the FHS, I would just like to see Linux standarize on one (again I am dreaming)
Assuming the USP becomes a reality, the FHS wouldn't really matter then...at least for installing packages. But for day-to-day system administration it would be very nice to have all systems laid out the same.