A friend of mine has got it inside his along with DJI zenmuse h3 2d gimbal and all extras needed. He also has his fpv tx installed inside the shell looks pretty much stock on the outside but inside I have no idea how he got it all to fit.
I'd be worried that the fpv transmitter would fry something! The one that came with my Fat Shark puts out some mean heat and having it enclosed like that could be trouble.......
My Immersion TX gets extremely hot so it wasn't even a consideration to put that inside the Phantom shell. To get more room inside the shell perhaps you should wait for the DJI Phantom Upgraded LED & MC board that integrates the PMU v2 onto the board: http://www.rcgroups.com/forums/showthread.php?t=1958557