Donald, apologies for late reply. I've been quite busy and then forgot to answer... anyway
If it comes to the issue you're facing now I think the only way is to enhance already existing code to support another expression language or do it just for your cases. Regarding the first one you have already found the place:
modify SequenceFlowHandler's end method to include your language of choice while parsing the BPMN2 constructs.
The other one is to:
- implement your own handler (that could extend SequenceFlowHandler)
- implement SemanticModule (that extends BPMNSemanticModule) that will put your new handler in the right place instead of the default one
- implement BPMNProcessProvider that will setup all semantic modules that should be used while working on BPMN processes
- last part is to register your new provider on BPMN2ProcessFactory
Hope that gives you some alternatives but unfortunately I did not have enough time to verify all the statements...
In my opinion you could go for the first one and modify core code base so others could benefit from your work
Good luck
Maciej