You're talking like it's a bad idea but you've listed several reasons why it's a good one...
i never seen any trojan or virus trying to infect a computer with the name mIRC.exe
Exactly, that's because they rename the file to make it look like an important system file that shouldn't be deleted. If it's called mIRC.exe then there's no chance of it being mistaken for anything other than mIRC, making it less likely to be used to help a virus/trojan proliferate. That's good for mIRC and everyone else.
you even can rename ICQ.EXE and still get it to work, and i belive many viruses and trojans are infecting you true that program too
The makers of ICQ have made it quite obvious that they don't give a damn what happens to their users or anyone else by the complete lack of security in ICQ as a whole. That's not really a reason to help make mIRC a tool for trojans is it?
i havent seen any script out there that had its own mIRC.exe named just mIRC.exe .. they renamed it to "script name.exe"
Including the exe with a script is illegal anyway.