As for your idea of having a game option to disable the black market: I'm intrigued.
I was involved in another topic several months ago where we were discussing possible changes to the black market, and this was the big stumbling block we came to for every proposal: the more you limit the black market, the more severe a shortage of a particular resource becomes. I'd have to agree; there are many otherwise fine start locations currently that would be unplayable without the black market.
The big problem essentially comes down to map randomness. It's nice to say "find a buyer" to someone who has excess metal deposits near their start location, but a buyer may not exist. If everyone else is scraping by for metal, you might only sell a small fraction of your excess. On the flip-side, no one may have a large excess of crystal, and you have no ways to deal with your shortcoming.
Consider other RTS games out there with multiple resources. You either have games like Warcraft or Starcraft where each map is hand-designed to ensure that the types of resources are balanced in appropriate proportions, or you have games like Sins where there is some sort of market feature. I think you'd have to hand design every map (down to the extractor level) if you wanted to turn off the black market.
