Yes, would be unusable otherwise, I guess.
great, thanks lowpo. Wonderful looking board btw

It should ship with those markings on it (ie, without the alphabets but with the cursor control and shortcut markings).
One more question: will your Fn key's keycode be recognizable (and capturable) within Autohotkey so that people can use autohotkey to assign/bind further shortcuts to your Fn key?
Looking at the layout now, I'd rather move Ins to the right of Del and the three rarely used ones to Q W E to reduce the clutter. I'd rather have empty keys around shift, enter and backspace. Less typos that way.
I think thats a good idea.
Also one more suggestion: Fn+x/c/v = cut copy paste. I find generally moving fingers to control key for those forces one often to look down to put index finger correctly on x,c,v. Whereas with the thumb-actuated Fn key, index finger, middle finger, ring finger, can fall naturally onto x,c,v.
another suggestion: Fn+s,d => forward/back (browser media buttons)
and, perhaps, also Fn+r = maximize window; Fn+f=minimize window.
Anyway I think that covers all the major navigational things.

You're right tho about finding the right balance between essential functions versus not over-complicating the interface. Some trial-and-error and 'tuning' work will clarify where that balance is. You can always practice your set up by putting it into autohotkey and seeing how it 'feels' to you.