The first issue you are going to run into is that if you follow the OMG BPMN2 schemas is that OMG does not really consider implemtation/usability when creating their specifications. Tools supporting BPMN2 almost always have to work as close as possible to the specification to make it actually usable.
If you are looking for a "bang for a buck" which I think if you put any work into it should be considered, IMO, putting time and effort into porting the graphical editor features of the Eclipse jBPM tooling into another IDE would be best. The subset of users who actually will want to look and edit and learn BPMN2 by looking at your pretty syntax highlighted code is IMO very small compared to users who would want to graphically generate processes...but again it's just my opinion :)