9 0 + sounds like a smart solution!
I am actually going through my key commands file now because there is something in it that causes problems with typing } in engrave mode Cannot type } in text frames - Dorico - Steinberg Forums
So I am recreating the key commands, cleaning up and reconsidering. Probably I will share it when I am done, but I have a strong feeling that this is a “to each his own” thing.
Regarding the flat/natural/sharp shortcuts, I just added “+” for sharp. Then I have
0 = natural, + = sharp, - = flat
Does not lie as nicely under the hand, but it has its logic anyway.