I can definitely agree that it would be nice to see some of the others races receive a more upfront spotlight. If we could get a salarian on our squad, one that will last for more than single game (like Garrus and Tali), I think that would be awesome. Perhaps we will even gain the opportunity to have some squad mates from races that did not once accompany us in the trilogy, such as batarians, vorcha, volus and so fourth.
As for the average crew of the Tempest, it would be great if they avoid filling it with a pure human crew, like they did with the Normandy, and make it entirely multicultural, instead. I want to see salarians, turians, asari, volus, elcor, hanar, batarians, you name it; I would accept just about any species on my ship. The possibilities have me excited.