I have read it; perhaps the problem is you only read part of it:
Would it be easy to write a script for my idea?
If it's something that is very easy to do with scripts, chances are it won't be built into mIRC. (This isn't always the case, but should be considered when posting your idea.)
Seeing as how qwerty already gave you the code, "I don't know COM" is not an excuse, simply use his, and looking at his code you can see it is ~10 lines, I'd say that is "easy" and "simple" and therefore shouldn't be implemented.
You are right saying "you can script it" is not always a good answer, but if someone says "I want $n instead of $nick" should we all say "Well it can be scripting, but since thats not a good answer, I guess Khaled should add it." Or should we tell the user that he can simply make $n an alias to $nick, me, I think the latter is the more sane answer.