I believe TMCC has only the ground, if I recall correctly the actual command control signal goes through the house wiring. DCS puts the command control signal through the middle rail. I am curious when you say you have equipment that only runs command control, as far as I know both DCS and TMCC/Legacy equipped engines work with conventional control as well, the only command-control like system that doesn't support conventional is Lionchief, which doesn't use the rails at all, it is direct radio control (lionchief plus supports conventional operation).
One thing that has been suggested to me (I am in the early planning phases of my own project) is if you are even thinking of using command control, to keep that in mind even if wiring for conventional control now. So wire a ground wire under the table/track, ground metal mesh in a mountain, wire blocks with a future eye towards command control. Never hurts to read up on how it is wired, instructions can be found on the manufacturers sites or other places, worthwhile looking at how they work and wiring with an eye to that, even though you can retrofit it pretty easily.
As far as the time goes don't worry, I am in the same boat, has taken me many years just to get to the point where I am close to starting, having to get my basement space ready with little spare time, lots of things to do, lack of resources, etc, so I am in the same boat. And the nice part when people put up their ideas for layouts and/or ask for help, is how it helps others. My space is roughly the same as yours (mine will be roughly 9x13), and some of the layout ideas posted in this thread have been really useful to me, my own layout design will be influenced by some of the early designs with my own variations of the elements.