BlackKat

Definitely I would go with the Bley with the Light Grey sidewalks. The reason for the Bley is around here is roads are rarely true black (although not as light as the Bley) but also I find that in photos the Black is a little too shiny and reflective (I know that sounds odd) compared to the Bley which is more of a matte looking color. One thing you can note from amongst the many examples of SNOT roads is people actually set up their city blocks with indentations sized to fit 32x32 baseplates (or other sizes) such that they are nearly flush with the sidewalks upon which the buildings are built. Sort of a modular system making it easier to change things around, build the buildings independent of the layout before placing them, and making it easier to transport if you take them to club meets or shows for display.

Have you considered using SNOT bricks rather than tiles on a baseplate? I know you are working in LDD right now so it might require you to switch to MLCAD/LDraw for flexibility, with I am guessing the eventual intent being to buy and build in actual bricks. But in any case using SNOT bricks can give you a lot more flexibility for layouts from everything to road width to markings, and lets you do away with having roads that look like they're comprised of square tiles as the visible gap between bricks is less visible than between tiles. See the following example (not my Brickshelf page or my work): http://www.brickshelf.com/cgi-bin/gallery.cgi?f=164943

Well the idea with MLCAD for a large model is, much like official large lego model instructions, that one builds the MOC in pieces or modules. You build a part then save it as a model file, where it becomes essentially one large piece. This I believe also cuts down on rending as it no longer renders each individual part of the model. But regardless of whether that is true or not you are, until the very end where you assemble the modules, working with much smaller part counts. SR3D Builder might be great for all I know. But I won't touch anything that isn't MLCAD. I can't work without the four view panes in CAD software. Placing parts in a 3d only viewing environment is just not feasible.

Remember the giant dump truck set 7344 a la some of the larger Hitachi mining or quarry trucks. That was a pretty cool set. I think with some work and a few extra pieces you could convert 7632 into a larger crane suitable for a pit mine. Mind you this is strip mining and maybe not what the OP was referring to necessarily.

I would highly suggest using MLCAD in tandem with LDraw instead of LDD. www.ldraw.org It's much more flexible and powerful than LDD, but at the same time it is more manual and complicated. Still it allows for models to be built in component parts which can then be placed together. This is a must have both because of the slowdown a large number of pieces would give anyone but those with the most powerful computers, and from a viewing standpoint of being able to see their whole model at once in any sort of detail. You can use MLCad to generate step by step instructions and export the parts lists so that those parts can be purchased either through Lego PAB or resellers such as those on Bricklink.