graphic desingner and programmer cooperation

We decided that our game will be based on physics. To make things go faster and to ease cooperation between me and graphics designer I decided to build game editor. Game editor will be based on Adobe Flash and Box2d library for that platform. When it's ready, graphic designer will set elements in editor (placement and physics properties), then he will click save button and xml will be generated. Xml will describe all elements on one level, so each level will have its own xml file.