i sdont see how taking out dcc is going to solve anything. people will just use other chat clients, or use older versions of mirc.
www.mircx.com has every publicly treleased version of mirc available for download. also as said about XDCC bots. they are more wideley used but mostly for large files such as programs and movies. but mirc is usually used more for mp3 in my opinion. and most of the good mp3 serving scripts are made for earlier versions of mirc.
illegal filesharing has not dropped at all. as the record labels start sueing users. the more of a hype it becomes. kinda like a online riot.
that being said. all in all. excluding dcc wont solve much of anything but cause more problems.