I apologize for digging up an old thread but I think I've come up with something that may add to this theory.
To begin with, I think the story of Cinderella is simply meant to parallel Moriarty's plan to portray Sherlock as a fraud. Cinderella involves deceiving people into believing that the main character is something different than she normally is.

On rewatching the episode, one thing that kept bothering me was the constant emphasis on the word "you". Mostly from the rooftop scene, the lines that stuck out were:
I O U (obviously)
I am you
You are me
Without me, you are nothing

Switching to symbols, I think its just a basic logical substitution:
I O U
I=U
U=me (also URme)
Without me, U R nothing (or, URme - me = UR, or UR(nothing))
extending that, the original message becomes UOme or You Owe Me, the commonly used opposite of IOU.

Most importantly, though, I got to thinking of the significance of "R" and "me". Continuing with Joalro's method of substituting numbers for letters, we have 18 for "R" and 18 for "m(13)+e(5)". The 18th story in the Grimm's tales is the "The Straw, The Coal, and the Bean", the synopsis from wikipedia is as follows:
An old woman has got some beans that she intends to cook over her fire. Being in a hurry, she grabs some straw to make the fire light faster. She pours the beans in the pot and, being in a hurry, she drops one on the floor which lands next to a piece of straw. Soon the fire is burning nicely and a hot coal jumps out and lands next to the straw and the bean. They talk and realize they have all narrowly escaped the fire; they band together to flee. At a river, the straw lies down to let them cross. The coal, being hot tempered by nature, immediately sets across. But when the coal is halfway across, the water rushes underneath, and the coal becomes terrified of being drowned. So he stops, too afraid to go on. The straw catches on fire from the coal, and splitting in two, the straw and the coal are swept downstream.

The bean ca