I'm not sure you can get a realistic mechanism without having large numbers of participants. Otherwise you just get colluders managing prices. That might make a good game, but it's not much like what you're asking for.
But what would be a good number of players to give you enough market variables, without being too many that the game suffers in the long run? Plus, in terms of gameplay, what if buy-outs and takeovers force players from the game? How much "fun" would be had by the player elimination?
