Right now, the Preview panel, Editor panel, and Scene panel are all in the same window.

It would be great if these could be 3 separate windows. This way, if you have 2 monitors, you could have the editing panel open in the full space of one monitor, and at the same time, have the preview window in another monitor - with the ability to resize each window to make the full use of the monitor space.

A portion of your request is already in the product.  You can do a "Full Screen Preview" to a second monitor.

Being able to "undock" items like the Scene panel and stuff is a cool idea.  Hmm... I can picture a 3-monitor setup already. 

This feature request has my full support!

Even if the 3 components of the edit window have to remain on the same monitor/same window, each component "box" should be individually resizeable.

I run 2 x 24" widescreen monitors with full screen preview on the second monitor.  But I am stuck with having part of the screen on the main monitor taken up with the small preview box.

Give the user full control over what is displayed on their monitors!