First, it's important to accept that very little ("almost nothing") about the BUSA eindecker is "scale" in the sense of really being like the Fokker EIII. It is strictly a "fun scale" rendition that's easy to build and fun to fly.

That having been said, there are several things that you might do to develop your WWI building skills and to give the model a bit more of a scale feel. Have a look at the following website for some ideas about basic mods. At the very least, I'd replace the "slab" sides with sides made from longerons and uprights/diagonals and install a pull-pull control system on the rudder and stabilizer.

http://www.angelfire.com/indie/aerostuff/eindeckero.htm

In the photo below you can see my EIII above a BUSA eindecker. I bought the BUSA eindecker kit, built the wing and then scratch-built the rest of the model based on scale drawings.