Maelstrom weapon is also a resource. It’s just built less reliably and is fully depleted by a single use.
I’d prefer ways to more reliably build it and to be able to store beyond a single use.
Another way to accomplish that is to allow maelstrom weapon stacks to build to 10 while still costing 5 to make something instant and by building maelstrom stack generation into one or more damage abilities (e.g., rockbiter builds 1 charge, stormstrike builds 1 charge, wolves build charges, etc.)