Behold, a theoretical crossover so amazing that it will send out nerd chills to anyone who views it. The current Doctor, Matt Smith, is trying out his very own Omni-tool, and if this wouldn’t be the greatest crossover in sci-fi history, I don’t know what would.
What’s that you say? The Doctor has already been to the 22nd century and there were no Turians or Krogans there? Well, then he could just jump into an alternative universe where they DO exist. Doctor Who has never been exactly been restrained by the bonds of continuity or reason.
This will likely never materialize, but we can dream, can’t we?