It seems you will need to hack your own solution. The class in charge of deadlines and escalation is: https://github.com/droolsjbpm/jbpm/blob/master/jbpm-human-task/jbpm-human-task-core/src/main/java/org/jbpm/task/service/DefaultEscalatedDeadlineHandler.java
Starting from line 187 is where the escalation logic takes place.
It would be good to have a pluggable mechanism to add custom logic here. Something similar to WIHandlers, but for the HT server.
Best Regards,