I'm thinking 4 stacks with 5 apps in each would be more than enough. Then the main part of the home screen could hold the original iPod/iPhone apps. Very nice.
Pretty cool idea, but I like the idea of the icon on your home screen. Unless of course, you don't like all the clutter. I probably wouldn't use it, but someone try it and tell us how it works!
I like a lot of these ideas, but they fall apart for most people when they go to use them. For example, I loved the idea of the starburst Dock, but after installing it, I quickly uninstalled it probably before the day was over. I'm betting that when Apple finally gets around to allowing more apps into the system, they're going to have a fairly clean solution... possibly similarly Leopard-esque. They always get boffed for stomping on developers' work (even if that work is derivative from their own), so it should be amusing to see what happens.