I'm not sure how much this improves your deck... having Copper instead of Estate in your hand is slightly better; but you'd still really rather trash that Copper. And if trashing is available; I don't think you'd take the time with this to avoid losing the Estate points.
Then again if trashing isn't available; turning an Estate into a Copper is kind of like gaining a Peddler.
I wonder if it would be better and still balanced if the Copper were gained to your hand?
I considered this, but I think that that'd make the card way too strong. Imagine this:
T1: I open 4/3. Buy Traveling Agency for $4
T2: I get rid of my first estate and hit $4
T3: I draw CCCCE. Bye bye second estate and hit $5
T4: I draw CCCCE. Ok, my estates are gone, and I hit $5 again.
This project isn't that great at getting rid of estates, but it can remove cards simply by drawing them. Staples likes that. Pooka likes that. And remember that sending to the island mat =/= trashing. It can effectively make a singular province produce $1, AND make it trashable.