Hi there,
I have worked for Square-Enix London for a long time and I am an expert Game Designer. I can make full GDDs for your games, although I am not a coder or developer. If what you´re looking for is a Game Designer, I qualify for this job very well. Sorry to point that out if you already knew the difference between developer and designer, but seems in this website only a few people can tell the difference.
Take a look at my feedbacks about game design in this same website, they are all flawless.
Thanks!
Hugo