I think you should add an new option to the /font command, to set one font as default font for all windows.
/font -e 11 tahoma
/font [-e [channel|query|chat|status|scripts|notify|and so on]]
This would be very helpful for theme builders, because you needn't write a large script, that sets the font as default font.
think about this idea
p.s. sorry for my bad english...