While I understand what you mean, this is not something which is dynamically handled.
If you go to the Popups section in the scripts editor (Alt+P) and select Nick List from the View menu, you'll see that the standard command there is: /mode # +ooo $$1 $2 $3
Naturally you can adjust this to include $4,$5,...,$n
Alternatively you could try to catch raw 005 and set a network-specific variable to adjust this to whatever value is permitted.
mIRC *could* be changed to do this automatically and this may count as a feature suggestion in your case. However, if I remember correctly, the contents of raw 005 is not consistent and uniform enough across IRCds for this to work.
