Needed: Sculting Brush: Erase Sculpt (for use with Multiresolution modifier)

How many times have you wanted to just erase an area of sculpting that you have done and start again with your original mesh? I can't tell you the number of times for me, but maybe that's just me! :) Most of the time I just use the smooth brush, then sculpt the detail close to what it was and start again. If I really mess something up, I go through the process of selecting those vertices, separating them into a new mesh. Delete the multires modifier, rejoin to the original sculpted mesh, remove doubles, and resculpt... ugh. It works, but man would it be easier if you just had a brush whose sole purpose was to restore the vertices to their original position.

I am not 100% sure about the ease of this, but to my coding ignorant self, it's obvious that when the multiresolution modifier is added to a mesh, that all the original mesh data is stored. How else would your model be restored if you removed the modifier, whether a part (like my method above) or just removed from the whole mesh?

So, since that is stored within Blender, could it not be used to sculpt vertices back to that position? A brush would simply move the multires vertices back toward the position that they would be in if the modifier was first applied. Another option that could be added would be to select vertices and be able to choose "clear sculpting data" again working only on erasing the multires data and reseting those vertices to their natural positions.

Honestly, I'm wondering if there is a hiccup that I have not thought about, because if it was as simple as I think it would be, I'd be surprised that it hasn't been added yet.

This could also be potentially added when sculpting a normal mesh, but that could be more complicated, necessitating saving data for an "initial state" of the mesh and also would have to be decided on whether to only save that data for that sculpting session (until the next time you drop out of sculpt mode) or something more permenant. Definitely a little more murky than with the multi resolution modifier.

Thoughts? Ideas? Would love to hear them!