you are not confined to use the CommandBasedWSHumanTaskHandler. You may develop (and if you are serious about jbpm you will probably have to) your own implementation of WorkItemHandler. As a matter of fact, WS-HumanTask specification is not a part of BPMN at all. In my opnion, WS-HumanTask is overgeneralized description of human task life cycle, using it makes sense only if you use a complete WS-HT compatible package featuring user interface and user interface development tools. If you plan building your own user interface, introducing WS-HT server component would be probably unnecessary complication.
re. Your new approach seems interesting. Have you considered releasing your work publicly?
It is released as open source (Apache v. 2.0 license). Just check my profile for the link. I interested in further info, I would suggest using PM, this is jbpm forum after all.
By the way, to avoid false impression of me criticising jBPM: I have spent several months implementing pilot projects using several open source BPMN engines and, if forced (by customer, contract etc) to pick the winner, I would stick to jBPM - it was the only package I was comfortable to work with. Not a completely "smoke and mirrors" (Bonita), no ties with VMware/Spring (Activiti), based on mature software (Drools), to be supported by JBoss (at least this is what mentioned several times here)...