This small mod is not very serious, it is silly and was quickly made.
This is so silly and crazy, I just had to release it!
I made Fluttershy and Rainbowdash smaller, or else you would see a very massive pony. When you mount her, however, you will also shrink while mounted.

Both are standing at Anvil stables btw. 

Rigging such a mesh so off of the normal horse mesh is not very possible, so there is some deformation. But not too bad.