Good question. You identified what feels like a problem to you. But the system isn’t impotent. In the Enforcement of Judgments Act (Code of Civil Procedure § 680.010 et seq.), your state provides as large an arsenal of enforcement tools as you will find anywhere. You can start there for your “ALL” and find it here:
http://www.leginfo.ca.gov/calaw.html
I have even less regard for asset exams than you do, but it seems to be everyone’s knee-jerk answer, doesn’t it? And do your attorneys regularly enforce judgments? If they don’t, recognize that podiatrists know enough (or too little) to practice heart surgery too, but they’re all doctors. Find someone who specializes in it.
Aside from saying that your debtor has an online store, you don’t say enough about what you know, including who runs the site, who handles payments, where they’re remitted and how and when, but the answer to “can you tap into their merchant account and take their sales?” is “The tools are there so ‘yes’ until you find that you can’t, and then you look elsewhere”.
Don't want to cut you off, if you have a need to vent, but, on the bare facts given, your problem is not so unusual or difficult. Using tools that are more advanced than an asset exam or a bank levy just takes knowledge, experience and hard work. And it can cost more to accomplish than the really simple stuff; assignment orders, SDTs etc. - they take more effort. But it's not heart surgery either. Get a pro.