The settings page is not static. You can already specify a path, see /help Command Line:
-i<filename.ini>
Makes mIRC use the specified file in place of mirc.ini.
-r<path>
Sets the data path where mIRC saves mirc.ini as well as other files and data. If -r is specified without a path, the path is set to that of the mIRC executable.
mIRC will also use the path of your mirc.exe as the settings directory if you put the mirc.ini alongside the executable. However, this does not work under default settings in vista when mIRC is installed to C:\Program Files\.