This is how my new desktop is set up.
There are six panels. I could reduce it down to two but I wouldn't be able to keep the items on the middle panels centered.
I think the most ideal hide/show behavior of the panels would be to hide when a window in the active workspace is maximized, and show otherwise.
The second most ideal behavior, I think, would be for all panels to show/hide at once when the cursor hovers over any one of them.
If that isn't doable, then surely a key-combination could be used as a toggle?