i know where you're going and i agree that the audience for this feature is not the majority yet not a small one. Of course the blowfish integration should be carried out non-intrusive. IMHO A "Blowfish Encryption" submenu with informative confirmation dialogues for the individual functions would account for unaware users.
The in-memory blowfish addon does not fix some of the issues i mentioned, like trustworthiness of source and it's also only good as long as memory locations do not get changed. Though i agree that the approach is much sleeker than the previous ones. The thread on the FiSH forums made me read this thread in the first place by the way and i thought it would be sweet to have this available as a mIRC core feature.
I think it's a good thing to be able to talk safely to colleagues and friends without having to worry about a man in the middle. As much as i trust IRCOPS i value my job and i don't like talking about business strategies or in-development technologies over insecure channels. This encryption scheme is not only useful to terrorists (;)) and i'm still sure there are others who would agree who currently don't even know this kind of encryption is available at all.