@Mayo Master - About developing a "sandbox" midgar, this would be a massive undertaking and believe me this is purely from speaking from experience. I have been with the "Mako Dawn" project for some time, having seen it gone through a few iterations trying to undertake exactly what you are suggesting.
The main issue you will encounter is scope. We have thought about most of the issues you have mentioned, such as sector purpose zoning, *had a nice graphic we made, can't find it atm*. When you start going into the macro-scale things like the (water treatment, garbage incinerators, steelworks, concrete factory), all of which are very important considerations but if the aim was to actually develop a project then, do that in the design stage, then limit that to a fraction of the area. Trying to remake a sector in my opinion is far too large a scope for any one project without considerable boundaries in place. The most recent iteration of the project for example was moved to doing the interior of the Shinra tower, which was then scoped to several floors of the known ones.
Even at that we were limited in what was achieved, which was in part due to actually getting work done, due to limited numbers of actual developers. This would be a major hurdle for any project to overcome, and our Lead Dev Tempus was basically a one man army. Getting all the ideas concreted is one thing, but realising them is a whole other ball game. Just because there are ideas, expect yourself to get your hands dirty.
I am not trying to dissuade you from doing it, just some friendly thoughts on the matter. I plan on reviving the project at a later date once I am ready again to start in the next round. One positive of this iterative process it that we are steadily accumulating assets, which we will freely make available, hopefully in the not to distant future. The other thing to consider is even though you might find a dev or two willing to help out, these things take time. Take a look at how long it has taken for the midgar models to be made, which are not targeted towards a game scenario and they don't have to concern themselves with the minor details of what is actually goes into the plates.
Anyways I would still be interested in hearing out your ideas and you are probably better to make a separate thread. Although I am not planning on reviving the project at any time soon, feel free to pm if there is anything that would interest. For anyone interested in the content pack that will be the final release for the current iteration of the Mako Dawn project here is some eye candy.