That's the thing. I don't think you can make the desktop finger friendly. If you scale everything too big, you won't have room to navigate between your various windows comfortably. And if you can't do that, then what's the point of having the desktop?
The desktop is all about providing space for multiple windows. The more room it has to work with, the better. This isn't something a tablet will ever be strong at. You only have so much space to work with, and most of that space should be dedicated to a single app.
What a tablet needs is a better way to multitask. Something that works almost as well as what you get on a desktop, but still plays to the strength of the medium. Metro's dockable apps come pretty close to this. It doesn't give you as much flexibility as a desktop, true, but it does allows you to juggle two-three apps pretty easily.
If you ask me, what iOS needs is something like app docking. Something that allows you to...for lack of a better word...prime an app for easy access while you're working in another. Also it needs something very much like Mission Control in OSX. I think using this setup, you could build something that's touch friendly, allows for complexity, but still simple enough grandma can use it.
You're looking at the worst case scenario. Touch based devices don't necessarily have to be any less powerful than their desktop equivalents. They just have to be designed differently.
And like I've said in the past (I've been repeating myself a lot here recently), touch will one day be the primary method we interact with our computers. A whole generation of kids are growing up around iPads, iPhones, Android devices, Windows touch enabled laptops, all kinds of stuff they navigate through with their fingers. They're gonna be expecting it from here on out.
Anyone who tries that deserves the headache. I use my iPad and Pages/Onenote/Whatever to write stuff all the time, though. I'll set it up on my desk, take my bluetooth keyboard out, and type away. And you know, it works pretty well. I could easily see a future where I'm getting by just as well as I am now with touch based devices.
...though you know what would make it better? If I had a damn mouse or a stylus with a proper pointed end for those moments when I want to make a specific selection. Touch pretty much sucks for making precise selections.
