Actually, quite a few renowned Great War aviators were "old hands" (comparatively) during the war.
I don't have my sources with me, but I know that the bio's in Neal O'Connor's books name a few people who were pre-war fliers.
From my mind I can hardly think of any.
was a pre-war aircraft designer so he must have been able to fly.
I think Berthold was in the Fliegertruppe as an observer before he became a pilot in 1915. Berthold was the observer who spotted the gap in the battle of the Marne in Sep 1914.
There are many more Germans (not much sources on the Allies on my bookshelves), however I don't think I'd be able to send them to you before you leave. I have a busy weekend ahead and I'm on my way to Spain next week so unless you're leaving after say, the 21st/22nd of July, I hope somebody else can supply you with the info.
Incidentally, what does your dissertation deal with exactly?