Right now most if not all IRCU's support many more modes than the few displayed in the channelcentrallwindow (doubleclick on channel), For instance, many networks support the +c mode to enable colorblocking and such 'new' modes.
Seeing that the used modes on a network are reported on connect in most cases (AFAIK), it should even be possible to dynamically add them as options.
The present fixed selection of modes is starting too look pretty dated in 2004 I fear.
