Would a "designer as a tab" aka "unified window" or "one window" IDE be possible?
Ex:
The ToolWindows would require some changing, like having the ability to dock designer Tool Windows in the main window. Another thing that would need to be changed would be if the designer tab is inactive, then either auto-hide or put a label that displays "Designer not active" in the Tool Windows. The script tabs wouldn't need to be moved; they could still be located in the designer tab.