I'd be interested, Maz, in both a cartoon+line Freestuff version and the fully textured, Poser-ready version. I love scenery construction kits. So many possibilities!

I've been planning to do some line-art-style fantasy renders and animations, and what you have in mind would really save me some time and effort.

As for question 3, I have two suggestions: spiral stairways (the ones I build never look right), and vaulted ceilings.