[quote=@AeronVex]We can do a replace-Normandy crew type thing[/quote]

Then we will have to have a human Spectre. The Normandy belongs to the Earth and it's military. They would not turn it over to another species' military for them to use.

Turian's could build their own Normandy but it would be the small outdated version from the first game and easily defeated by the human's larger more advanced one. But for it to have a multispecies crew again would have to have a turian Spectre.