Using salience with parallel agenda is probably not feasible, because salience is ordering of rules and ordering introduces rule serialization. However we should discuss this more so we know 100% that there are no feasible solutions.

One possible scenario could be to put all salienced rules (and relatives according to rete) to separate partition, which is handled by separate agenda and process this agenda before all other agendas. In such case these "other" agendas could be processed in parallel after the "salienced" agenda is processed. Other name for this feature could be "postponed partitioning". First process everything that cannot be partitioned and then process everything that is partitioned in parallel.