I don't see how that would make me not like sleep considering that halkun's experiment sort of makes it a lot more possible on a much shorter time-frame, all you really need to be able to do is trace and upgrade the models one area at a time much like with the characters.
As a rule environments have a lot less detail involved over character models and less detail = less time spent however we would need a texture artist to do it properly.
think about it we could place our own mark in midgar, put boxes places they weren't making the game more modding friendly/higher detail
epic fail on this post. While "tracing" the backgrounds can be somewhat quick, it's still a very tedious and time consuming process. Then you have to export the model, unwrap a mesh(assuming your going for 3d rotation in game) and get an ace texture artist to basically re-hand draw the entire scene.
Now your done with the opening train scene, hopefully it only took you a month of dedication and no free time.
Even re-rendering the scenes in 2d will require someone to take the completed sketchup render and create brand new textures for each face as well. Yes, this method is easier, but that still doesn't make it "easy" to do.
Download sketchup and gimp and give it a go for yourself, you'll see very quickly that your demands are quite insane. It's quite a bit harder to "trace" the image than you think.