It's news to me, but it seems there was some Mass Effect 3-themed DLC for Final Fantasy XIII-2 in the works. Given other recent moves, I get the impression that Square Enix is using Serah and Noel's adventures as something of a testbed for making DLC work with their major brands. EA is clearly glad to help, and the results are due next week, on March 27th.
In the meantime, look at Serah and Noel dressed up in gender-appropriate N7 armor. I have to say I'm mildly disappointed. About the only "iconic" thing about Commander Shepard's armor is the "N7" icon. And Ezio's Assassin's Creed: Revelations outfit is easily fabulous enough to fit in with a Final Fantasy game. Personally I wanted to see Tali and Garrus costumes, ones that change the character models to have three fingers on each hand and freaky-yet-kind-of-hot legs.