I've asked a couple reputable companies that do tranny upgrades for other platforms and they won't work on this one. Not sure why, they didn't say. Good thing is you can find used AT trannies for very cheap. Have you decided what you were going to do?
2011 335is DCT, JB4 MHD BEF, stage 2 LPFP, e50 50/50 meth, FBO, MT ET Streets when needed