Currently the only way to manipulate priority of BP instances within their execution queue is via the Execution Control Service.
This requires the BP to actually enter execution, and potentially have to traverse a deep queue, in order to apply the desired priority in the first place.
It would be more efficient if priority was an user-defined parameter
much in the same way as queue number, persistence, lifespan, etc. so
that priority is set when the BP is put on the queue, rather than having
to wait for execution.