Hi Richard,
With respect, your advice is entirely pointless. Suggesting legal action, when the client is probably a scammer sitting in a Vietnam (as example) basement, will achieve nothing other than severe legal costs.
Shopify needs a fraud team that can act immediately and investigate the claim, following which they should be shutting down the fraudulent clone.
The Shopify platform, by it’s nature, makes fraud very easy for any non-technical person to execute upon, and they therefore have a responsibility to wipe this out without cost to legitimate merchants.