You can get a full screen OpenGL of sorts. Under the View menu, there is an option for "Full Screen" that works only with windows other than the 3D window. (There is a button on the Windows tool bar, or the shortcut ctrl-\ toggles full screen on and off.)
The trick is that if you go into full screen mode before you switch to the 3D window, and then maximize the 3D window (if it isn't already), you basically have a full screen OpenGL 3D window! (So: ctrl-\ then ctrl-3)
Your comments about toggling the remaining palettes on and off are deeply shared ... many of us have been complaining and wishing for this for years. In 6.5, one keystroke could toggle all palettes on and off. This functionality was lost in 7.0 and above. You can 'fake' it by defining some adjacent keystrokes as the toggle commands for each individual palette, and then playing a 'chord' (well, an arpeggio - one key at a time) to toggle things off and on. Still a big wish list item for me to get this onto one key like the tab key in Photoshop.
I also agree with your comments about multiple named cuytsom workspace layouts. Cinema 4D has this feature and it is wonderful.
One of the forum moderators • AC 25 USA and earlier • MacOS 11.6.2, iMac Pro