You're basically confusing form (how mIRC improperly displays channel operator CTCPs) with function (what CTCP and CTCP replies are properly used for).
If there is a problem with how it looks or where it is displayed on the client, the client should be fixed to properly interpret the standard.
According to the CTCP standard, PRIVMSGs are used for CTCPs and NOTICEs are used for CTCP replies. Actions aren't replies and shouldn't be sent as replies.
will encourage a conformity in scripts and other clients that can't make up their mind.
Using CTCP ACTION is a standard to which all clients currently conform. Breaking that standard just because mIRC doesn't properly handle channel operator CTCPs would remove the conformity that's already there for no good reason.