You can't create complicated finger apps for the simple reason that we have now reached a new level of wasted screen space, no matter how high resolution your display is (those controls will just resize on higher res displays in order to allow finger access, so the only option is oversized displays for anything complex). Oh wait, the single pixel border saves huge amounts of screen space, so it should balance out. Right?
I stopped caring really, so I might be out of the loop on this, but can finger apps even spawn additional windows? For instance, if you wrote a finger music app, can you open the plugins in additional windows like every real music application on the planet does?
Wait, did you really just complain about proper DPI scaling? If you want your app to show more on bigger screens, then you design your UI to be responsive and show more when on bigger screens. This is all baked into the UA platform.
And I hate applications with multiple floating windows. They always get lost behind other windows or get in the way on top of something I'm trying to work with. Let me dock them in the main window, and have temporary dialogs slide in from the sides instead of popping up on top. There is no reason that a pro DAW could not be written as a UA (assuming they've addressed the horrible high audio latency present in Windows 8 WinRT apps).