It has been asked before, and in a manner, it can be done.
You need to make copies of the ini files for each user, then when starting mIRC, specify the directory mirc.ini file for the person going to be using mIRC. It's not perfect, but it does work.
If you just want to use shortcuts, you can have the shortcuts point to the ini file, but you'll need a different shortcut for each person.
