Hi Ben,
I agree that there's a lot of room for improvement in this area.
Just copying what another engine has implemented is however not our approach.
There are some good things in there, so it's definitely something we can work on.
Would you be willing to invest development time in this as well?
When you were referring to the Activiti BPM suite, were you referring to the commercial offering or the open source project?
In the commercial offering we do have support for consuming REST services in some places already.
Best regards,