I was very pleased when the warning dialog was implemented for when people click URLs, and I agree where feasible more protection warnings should be put in.
However, I think if you had to disable everything that is dangerous you'd end up disabling most of mIRC by default, and as for most people (i.e. people coming in from MSN chat clients) mIRC is already confusing as it is, it would only increase this confusion if they kept getting warnings every 5 minutes.
DCC warnings, /load warnings and clicking URL warnings already come as standard with mIRC - I'm still of the opinion that at some point people have to take responsibility for themselves, and if they don't, they'll have to learn the hard way. Internet savvy users can only advise and help people and people such as Khaled can only do so much to their software to protect people from the dangers that exist on IRC/Internet. Some people just don't care - it's not a matter of letting them know what could happen and they suddenly get worried, they know about it - they just couldn't care less what happens to their computers. I've got friends who download Kazaa/iMesh and I try telling them in lamen terms about spyware - they simply shrug their shoulders.
No matter how much security you add to something some people seem almost determined to get infected/exploited/etc - that is of course not a reason to brush off your suggestion, what can be done should be done for those who DO care and are simply not aware of the dangers as it's not fair to put them through the inconvenience, annoyance and time-wasting of dealing with an infection. However, just thought I'd comment on the practicality of it - the theory's good, but it's not going to be a miracle worker.
My 2 cents.
Regards,