Hmm, one more thing. You said in a previous post that all the races would be in the same sector of the galaxy so that they would come into contact with one another.

That's actually not nescessary at all given that the mass relay network stretches across the entire galaxy and allows for almost instant travel from one end of the milky way to the other. (the quarian home system for instance is almost on the opposite side of the galaxy from council space yet they were in contact)

It is true the galaxy is vast but the network, while large, is alot more limited. I have no fear we'd not run into eachother.