That's how I see it too. First move had to be a sign that Mueller was outside his box. Next move has many options, and they are not all mutually exclusive.
Letters to Rosenstein from Team Trump, letters from Congressional Committees, who question DoJ (Mueller is part DoJ, just not subject to "regular supervision"), a public education campaign about the scope of Mueller's authorization, outrage about Mueller's with hunt - and make it personal. If Trump has dirt on Mueller, let Mueller know it's coming out. All the past failures, "Anthrax Mueller" comes to mind. Surrogates can go on a reputation-damaging rampage even without being told to do so, and that is coming.
Demand a completion date from Mueller. Put Mueller and Rosenstein under a microscope on this project.