Very interesting discussion here. I'm founder of a cloud startup and would love to hear your view on our solution:
We're currently building an API for rendering with the major render engines like V-Ray, Corona etc. Therefore we automatically scale jobs and deliver the results to our customers favorite storage like a NAS / s3 bucket or a google drive.
Another factor is, that we can reduce the costs for the cloud rendering factor 2-3x compared to the public clouds by tapping into spare capacity of secure data centers around the world (connected to our platform).