Thanks for all the input. We'll give it a go and pass along the results from our gameplay.
And to address the question Bob brought up, let's say, with built units from one factory, the factory can only produce that one kind of unit and must continue to do so, unless it takes 1 turn out of production (knocked/laid on its side) to re-tool at a cost of 6 prod. pts., which is what a factory would have to do anyway. That would be the case of each factory constructed, so two factories could build the same or different units, and would keep doing so to the end of the game, unless they retooled.
Mark, I'll be working on the oil field dimension too. I've got some oil barrel models (I got them on E-bay) and I think they're Axis and Allies Miniatures, even though i've not a clue where else you could get them from.