You sound like the only person who's dealt with this problem before :-)
I remember the Visual Studio setup team and their stories about the woes of trying to make downloads as small as possible. You're fighting with:
- wanting the file download to be one step
- what version (or sets of versions?) can you upgrade from? Does this include the one-off patches you were mandated to provide to top-tier (guaranteed bug turnaround time) Fortune 100 partners?
- how do you handle corrupted files or munged bits of the installation that were unchanged between versions?
The list goes on. You'd think things like Setup are boring, but trying to make the experience smooth and good requires and incredible amount of amazingly unglamorous work. It's one of those pieces of the product that nobody notices until it is slow/buggy/has picture of people who are way too happy to be using your product flash during installation.
