I would assume that making propositions should be beneficial to the whole, or more clearly stated.
DCC options has an internal idle timer, so does fserve. mIRC also has an idle timer for yourself.
Otherwise why would you need this? Quite frankly DCC chats should only be used for communications that you want to have right then and there, but I would imagine of course you want this for some sort of file serving functions.
Script around it, as this does not benefit the majority of mIRC users.