You've drawn it with a MOSFET, which doesn't multiply capacitance at all. Or, actually, following the same design motivation, it still is, but the ratio is nearly infinite; but that's absurd, and in practice, that means the description breaks down and it's better called just a filtered source follower.
You aren't apparently filtering anything the LM317 won't handle, so I don't get the point in the first place.
How does an opto fit into this?
Tim