I was just about to post that this entire story could have been completely transposed to almost every conversation I've had in Los Angeles over the past year and a half. Looks like you beat me to it!
This debate should have started in earnest even before the Matrix sequels - digital crowds were used extensively throughout the 90s (Digital Domain's work on Strange Days and Titanic being the big examples) and the guilds have at least had some knowledge of these processes.
Believe it or not there was a system at Sony Pictures Imageworks that worked like this - no idea what it was doing under the hood though. Worked great in practice though - every possible production resource was a URL that started with spref:// iirc.
Recent enough - at a Google event earlier in 2018 it was mentioned that GCP was now compliant with most (if not all) of the major studios’ security requirements.
You described most of the goals of Sandstorm (https://sandstorm.io/). I don't think they've really landed on the right user experience yet but I imagine they're definitely working towards improving it.
I can speak to this happening at a major visual effects facility in the Los Angeles area. There was one developer (a guy who developed Academy Award-winning volumetric rendering software) who was able to live out of a mobile home parked in the main parking lot. This was around '99-01 or so - they're no longer in the same location and I'm sure the current ownership would throw a fit if someone tried it today. You could pretty much get away with anything at Venice Beach in the 90s.
The infrared makeup (pretty sure the only company that kinda pursued that path was Mova) was kind of unwieldy and it's kind of fallen out of use already. Most facial capture in the future will probably just utilize some kind of depth capture (light field, structured light) in concert with a normal witness camera to reconstruct facial features.