I've been thinking about how to port my favourite window manager to Windows 7: Openbox. And I've realised that the easiest port would be possible if someone had figured out how to port Xorg to Windows 7 as a shell. We see alternate shells like bb4win (now called bblean), they run off of whatever graphical system windows uses and the code is brand new, it's not blackbox, it's a complete redesign. A true *port* of blackbox would be tricky to accomplish because of its heavy dependence on Xorg (The graphical system that many *nix systems use). Putting it simply, this is how openbox would run on a linux system:
Hardware <- Kernel <- GNU Tools <- Xorg <- Openbox
Here's how I *think* windows does it (I have little knowledge on window's workings):
Hardware <- Kernel & OS <- Shell
It's likely very similar to that as windows is not modular like Linux, both the graphical system and the operating system are built tightly together.
Using BBLean for a little bit, I've seen that the graphical system can function without a shell (ex. Regedit can run, be dragged about the screen without explorer.exe running as the shell in the background).
To me, it seems plausible to have Xorg run as a shell and a window manager run in cygwin. I have done something similar with cygwin. You can run applications that depend on Xorg either in an X session that runs within a window, or have the X session run on top of the current shell as a standalone application then have the applications use that.
I may be quite possibly rambling here, but I'm wondering if someone has done anything similar to what I'm suggesting. BBLean is a nice shell, but it has many features built in, I prefer a more lightweight WM/Shell that does one thing, and other applications do different things (openbox is the window manager, you can use tint2 for the Tray, and nitrogen for the background setter, amongst other applications for other purposes). To me, it's simply much easier to have everything be separate and flexible so that each application can be easily configured (On BBLean, to set a different background, you must edit the theme file and set the path of the background, it's a slow process).
I'm a former linux user. Most windows users I know won't care about this kind of customisation, and would be more of a bother than a facilitator.