Maybe in the new one you can add a password thing which only locks the mirc it is set on, great for computers with multiple mirc clients. It's not needed but some people have to use shared computers...but mIRC is still none the less great.
Don't know if this is what you meant, but this would be nice too. A password to encrypt and decrypt all the loaded scripts, aliases, and the remote.ini so they can't be tampered with or looked at.