This is my idea for the "shelf" concept someone has suggested. I hope you're fine with me trying to improve on your design.
The Panel should be on the bottom, explained here. This way, the shelf button can bbe used as a hot corner to, well, display the shelf. Options for customisation can be being able to change the name (Shelf) and changing the highlight color when the shelf is activated.
How it works
The shelf will only display minimized windows, leave it to the overlay for more window management. Minimized windows will also use the same coloring system I've developed explained here. There can be arrows to indicate that if you mouse over it will show more minimized windows. But there should be an option to make the shelf smaller if the user wants that instead of mousing over one side to find more windows. And the user should have to click outside the shelf to close the shelf to prevent accidental closing of the shelf. When a window minimizes, it should be placed right on top of the shelf button, to give it easy access.
Theming and Animation
There should be options to theme the shelf, combined with the gnome-shell's theme. It could work by having different shelf backgrounds/grounds (the thing windows "stand" on) be able to switch to 3-D shelf or flat, change the way the arrow looks, and so on. The user should have different kinds of animations to choose from. A few options could be like the Mac OS X Magic lamp effect and the scale effect that windows uses. But they should also minimize (at least look like it) to the Shelf button (I know my mockup doesn't show that, sorry). The reason for that being it helps the user know that his minimized windows will show up if they click that button. And the shelf button should also flash once to give the user more indication that the shelf has done something.
Please edit this page and give comments, make my paragraphs more easier to read and whatnot.