Squeeze Dual Root With Single Userspace

I would like to run Debian with multiple roots and share the same /usr directory but am unsure if this is asking for trouble. My ideal setup and reasons are below: /dev/sda1 100MB /boot /dev/sda3 4096MB swap /dev/sda2 400GB LVM LVM broken up as: Root_Stable 75GB Root_Testing 75GB USR 50GB Home 200GB I have my stable 2.6.32-5-686 default kernel for backup with a grub entry to boot the system with either Root_Stable or Root_Testing. I also a working 3.1.5 kernel that can boot with either root. The whole point of this is I do a lot of modifications and mucking about with the system in general. As I only have one computer so my Root_Stable is a standard netinst install with no modifications while the Root_Testing is a custom debootstrap with no SELinux support. As things become stable I shift the mods into the Root_Stable pretty much the same way Debian has its releases set up. The main thing I am worried about is how to share the /usr directory. I want access to my applications regardless to the root I am using but I do not know of the many interrelations that are going on in the background and if I ran two roots would apps freak out and start mutilating my data? Wine is a good example, I built from source and installed in /usr/share/wine and it worked great. After a few boots around the different roots now wine does not even load when run from the command line. Is thing an expected side effect of how I want to do things? and if so should I just run two user directories after all? Thanks!!

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