Thing is, in order to make that work you'd need to restrict applications to managed code to keep CPU architecture out of it and, if you wanted things like the ability to transparently save data to the phone, additonal restrictions like forcing file access through Isolated Storage. You'd have to have an enormously ambitious and long term vision to bake those kind of things into a v1 product.
I really don't see what is so "enormously ambitious" about this. If you take the WP7 SL+XNA version and adapt it to run as a full-screen framework on Win7, why would implementing things like IsolatedStorage be so difficult? It could be essentially a sandbox where the only API the apps will have is what's in the WP7 version of SL+XNA. You can't P/Invoke in WP7, so why should this change when it is run on Win7? The storage related classes will work just like the ones on WP7.
Anyway, I think people somewhat misunderstood my initial idea. I wasn't thinking about tablets that are as "lightweight" as the iPad, I was thinking about tablets that can already run Win7 as is. This is a way to make it more attractive for consumers by providing some of the simplicity of what people like about the iPad. Since W3bbo asked specifically what advantages SL+XNA had in this case, this is what I'm thinking:
- With the recent interest in WP7 development (read this blog for instance), making it easy to bring those same apps to existing Win7 tablets (and newer tablets) would give them a user experience that seem to be popular outside of geek-minded consumers.
- Have you seen the WP7 development tools...!? Compare to other development environments.
- Compare how apps are installed/uninstalled in iPad/iPhone/WP7 to how it is done on Win7. People really don't want to go to Add/Remove programs and search through a long list of confusing products to uninstall something. They want to press and hold its icon and choose to uninstall it.
- I always feel that I don't want to give up the ability to run some of my favorite older desktop apps or games on a tablet. You need just one such an app or game to make something like the iPad a no-go. So having the ability to still do that is important I think.
- EDIT: Access to the Windows Marketplace, in a similar way as you will be able to do with WP7. Finding/seeing reviews and ratings/buying/installing/uninstalling tradional Windows applications is a PITA.