Just as a quick aside, about one of the things 
you said... "A cels are drawn by the key 
animator. B, C, D, etc. are drawn by in-
betweeners, and so might not have as high a 
drawing quality."

It's my impression that the lettering applies to 
the layering... if there are three different cels 
in the same shot, they're going to be labeled A, 
B, and C according to which is on top of what. 
And the numbers, of course, apply to the order in 
which they're filmed within the sequence. Key 
cels are drawn by the key animator, and are 
denoted by being circled on the sketches.

But back to fake cels. ^_^

-Cres