The only designs I can think of like that are VFW614, which failed, and Honda Jet. There are costs to counter the incredibly minute alleged increase in efficiency- much more engine noise in the cabin, a severely restricted view from the window, and possible fire safety considerations. Not convinced it is in any way worth the bother.
I have been mystified since the advent of the 757 why the extremely old 737flight deck shell design has been left a la 55-year old 707/727 layout as opposed to the cool 757 design, which is roomier, more visibility friendly, presumably less draggy, and gives commonality across all Boeing types up to 767. If the NGs all had 757 flight decks and windows, it would have updated the aeroplane even more. Now it's like having a sports car with a post war sit-up-and-beg windscreen!