At first I thought you relying on third party nodes APIs would become a bottleneck in your plugin development, but I didn’t realize how many 3D apps out there actually implement nodes (practically everyone that matters).
The help menu in Bella sends me to a web page which explains a number of bits and pieces of an elephant to a blind man, but doesn’t explain the shape of the elephant itself. So I am glad you outlined your thoughts here, since initially I was thinking Maxwell studio; just as you guessed. Maybe some of this explanation about the GUI could find itself in the FAQ section at some point (?).
Right now we are looking at a chassis, but I really like the amount of syllogistic effort you put in the ergonomics and design foundations of your apps. I think automation and simplicity that hides most of the gnarly esoteric detail from the user is the way to go (the opposite of Vray). I would even go as far as hand holding for Industrial designers and add a “studio” environment (next to color-dome and sky-dome) complete with a back drop and three key lights. Industrial designers would want to go from zero-to-render in no time. Despite popular belief I prefer simplicity myself; just slap a material and do “awesome” without having to worry about abbe and snell.
Heck, with AI these days I wouldn’t be surprised if rendering goes this way: