Hi Scott, I agree with what Vrit said.
Here's what I recall learning from helping package Picasa: - don't package the installer - rely on the system's update manager to pull updated versions of the package from the repository - install everything read-only into /opt/companyname/appname - start the app using a shell script that creates a wineprefix on 1st run - The wineprefix should have real directories (so the app can create files in Program Files, ugh), should symlink to all the readonly files in /opt, and have real copies of any files that can't be read-only As Vrit said, the script that creates the wineprefix is very app-specific, but once you write one, it's probably easy to write the next one. - If you are running your own repo, you should put exactly one app per repo. Otherwise you run into trouble because Canonical would want to review all the apps in the repo every time you update any one of them.
So no overlay filesystem needed, symlinks should usually suffice.
(Picasa also went further and bundled a snapshot of wine, too, and modified the app slightly to display unix paths, which required adding one little extension to wine. I'm sure the wine patch is around if someone wants it. And since it was in a non-ubuntu repo, it had to do a strange song and dance to avoid autoupdates being disabled when the user upgraded to a new version of ubuntu. This was considered safe because picasa was fairly well self-contained and maintained, and was unlikely to break on system updates.)
In case you want to look at picasa's scripts, the download page seems to be gone, but the repo seems to still be there:
http://dl.google.com/linux/deb/pool/non-free/p/picasa/picasa_3.0-current_i38... http://dl.google.com/linux/deb/pool/non-free/p/picasa/picasa_3.0-current_amd... 4ecf30186ce76430a7791cee2608f47e07b015e6 picasa_3.0-current_amd64.deb fe8e83b29a10b5d663e87861d85512faea036c06 picasa_3.0-current_i386.deb
Still installs and runs ok on 11.10.