We need a Instant messenger Function in Mirc.
No, we don't. If you want IM functionality, use an IM client. IRC and IM are very different things.
IRC was never designed to have 'buddylists', graphical animated smilies and the most irritating font colouring techniques imaginable just as IM was not designed to have channels and operators and kicking and banning of users by other users.
What you are proposing is, in fact, to take one product, totally mutate it from its original purpose and design into something else which was originally designed as a replacement for the product you wish to mutate in the first place. Don't you see anything wrong with that?