1+2. Cool, I will play with that.
3+4. I completely understand that for the majority of users (that work within arch and viz), physically correct is the way to go. But if you work with advertisement and vfx, that's not necessarily the thing anymore.
When I do images like this, I prefer going all energy-conserving:
http://www.superrune.com/gallery/images/2010_sozi_group.jpgBut when doing stuff like this, it's almost impossible to be able to find the physically correct values within your deadline:
http://www.superrune.com/gallery/images/2010_trolljegeren_01.jpgFor this job, I had to use different environment maps for different parts of the character. There was different environments affecting the GI and the reflections. I also had to have object that were only seen by the reflections in the eyes etc. There was a ton of cheats on this to be able to make the deadline, and this was a very simple job.
I worked with one of the agencies bidding for the logo of a major beverage brand, and when the art director asked for more intense reflections on one part of the object, it was just the simple matter of cranking them up. It would have killed my deadline to render them separately, take them into photoshop - gain them up etc.
Of course, my existing (now killed off) renderer does this. And there's a lot it doesn't do, that Corona does. That's why I'm always interested in new tech, and Corona looks
real interesting. So take it as it is, feature suggestions from an interested artist :)