The main issue is that because these popups have been in use for so long, they are likely in most mIRC installations, in the original or modified form.
One solution could be to make mIRC check for /modes that specify combinations of just +/-ovh and to trim these to match the number of parameters.
Actually, I could also make it trim the number of parameters to the modes, if too many parameters are specified. Just in case :-]
This will only affect /mode not /raw mode.
I'm going to add this to the next beta to see how it works out.