Choice is usually always good, unless there is too much of it. Here I think you're going in the right direction, with making it more of a choice where you take your third. But still, I don't think it is much of a choice for a zerg, as we tend to expand from the enemy and like quite open positions, just like the newly remade third seems to be (at least more so than before).
Terran on the other hand might be happy with taking either, the original third will probably be an orbital, while the middle expansion most likely will be a planetary. So here the terran will have to chose between a bit better economy, or a closer base which is easier to defend. And this is a good thing, I think.
I don't know what protoss wants though :/
PS. Did I just shoot myself in the foot by helping you here?
