Hmmm, well as long as there might be a sound event playing to alert the user (the idiot me) of the change to another function, I see no problem with monitoring the click length combined with location for different kinds of options.
For an example, clicking for 1 second on the bottom half might change a highlight color (with medium 2 seconds and or 3 seconds extra bright user discretions for colors) double click no highlight, meanwhile a top monitored click will change the fonts (again 4 different font options) with the double click switching back to the default font.
The sounds should be customizable though... Should I send you some basic sound wave files to package with the release? I mean all they are are beeps and whistles really but it would help with alerting which function is active.