I think he was saying, if you could do it in HKN, to win those people over, you would need to be able to do it in your new program. Like, round robin (toggle). If your new program can't do round-robin, it might not win people from HKN, since you can do it there. If you can't do white list or blacklist (I press "2" and only computer #2 repsonds to it or don't broadcast anything other than 1-0 and F1-F12), then it might be limiting. If you can't talk to multiple computers, again, probably won't win new people. I wouldn't worry about having to do everything that everything else can do. You can expand later, just get something that works first.
If you want to do something no eles has done, Mac and PC use hasn't been done. Mouse broadcasting has been done, but it is mostly a WOW thing (camera position and player facing) more than a broadcasting thing (my opinion).