If you don't want the desktop because you want to save that one click just don't go there! You can simply switch between the multitasking screen and apps without ever seeing the desktop.
That of course means that you'll always have to leave one app opened, but frankly I can't remember when I closed the terminal the last time.

I could rather spare the apps menu than the multitasking screen because everything I need is on my three desktops and for some things I don't need an icon at all because I start them from the terminal anyway (e.g. mc, vim).

I have no idea how much RAM it will save to completely eliminate the desktop, but I wouldn't estimate it to be more than a few kB. I think you can gain more free RAM by choosing a solid-colour background image.