I added a draw string closure to my MLD Newt a few years back (this was the first release of the Newt).
I didn't like the roll-top closure system on the Newt, so I cut it off and added a small extension collar with a draw string. The small extension collar more than made up for the volume I lost by cutting off the roll-top.
I also added a small compression strap over the top for when the pack is under filled. I used coated rip stop for the extension collar. I also added the large mesh pocket on the front of the pack which is why the pack looks so different in the before and after pictures.