Wouldn't you know it, there's also a
SolarPro article for that:
Module-Level Rapid Shutdown for Commercial Applications
After researching this topic and speaking to stakeholders, I think it's far from a foregone conclusion that the UL's new rapid shutdown safety standard will ultimately require module-level rapid shutdown. MLPEs will certainly be one type of system that can comply with whatever consensus safety standard gets adopted, but I suspect that string-level products like the HiQ inverters will also be able to reduce hazard to an acceptable level. That may provide an opening for string inverters with multiple MPPT inputs, as that would seem to reduce available fault energies. I'm just guessing, but I'd be surprised if UL develops a standard that only allows for module-level shutdown.
Otherwise, I agree with your basic line of thinking. It's difficult to justify MLPE in commercial applications. Microinverter systems don't scale well. Sure, you can do what APSystems has done and make a multi-module microinverter, but your basic building blocks don't provide a lot of opportunity for cost reductions as systems get larger. The SolarEdge approach seems to be more interesting because it allows for very long source circuits, which does enhance the platform's value proposition. SolarEdge basically argues that you can get the advantages of 1,500 Vdc strings with it's commercial platform, based on its fixed input voltage; best of all, you can use standard 1,000 Vdc rated components, which sounds intriguing. The TenK platform is also pretty interesting once you wrap your head around it. But you have to evaluate the platform based on LCOE and be able to convince your finance partner that the equipment and production estimates are bankable.
Great technology is only a piece of the puzzle...