That's an idea, pretty much what I wanted.
Personally, that'd be something I'd like. Though, I'd want numerous options like this. Specifically for messages.
If it was possible to add both a "Logging Format" box, as Om3n mentioned, along with either a seperate dialog or a section within the options dialog, to control the display of mIRC events (channel messages, priv messages, kick messages, etc).
This isn't actually necessary either, however, it would clean up a lot of scripting. Which would also make mIRC a little more visually customizeable for newbies. (ie: in the options dialog, a seperate "Visuals" area, which would allow you to customize: "Input: $timestamp $+(<,$nick,>) $1-"
I dunno, having mIRC handle these things (log formatting, event formatting), rather than scripting them, seems much more efficient.