I really like this idea, and I am a fan of the Mass Effect series and universe, but I can't help but think that I would like this project more if you tackled the licensing hurdle by creating a unique IP with many similar aspects of the Mass Effect universe.
In a better world, we could riff more easily off of ideas; but here I see what seems like a great idea potentially shut down through IP enforcement. Even if you do get the agreement that you seek, you are having to agree to the mandate of E.A., who doesn't have the best reputation in regards to respecting those working with them.
As much as I love Mass Effect, I think that you are better off creating an original product. I do see the benefit of piggybacking off of the fame, and your personal interest, of Mass Effect, but I personally would prefer this alternative, for whatever that may be worth to you.