It would be nice to see (AI-flyable if not player flyable):

HALBERSTADT CL.II (purdy pleez!) Just my opinion, but there seems to be a nice mid-to-late war niche perfect for this plane. This plane has a great many striking paint schemes

Airco de Havilland DH4

Breguet 14 (sorry... I know it has been described as a dead horse... but I just had to say it once.)

The Sopwith Dolphin would be really cool.

WOFF devs, Thank you LOADS for all the hard work you put into this sim!