I think it would be safe to assume most people would be using this w/ a 3 position switch…
Maybe don’t even give any options other than high/mid/low… (1000-1333, 1333-1666, 1666-2000).
That would work for 2 and 3 position switches, and having 3 options on a knob.
Of course, other people might disagree and want more options.
Just allow a comma-separated list of options in RcX_option (with 1, 2 or 3 values) and set PWM ranges automatically depending on list size: over 1800 for a single option, <1200 and >1800 for a double and 1000-1333, 1333-1666, 1666-2000 for a triple.
Channels would need some sort of priority set, so that modes would not interfere with each other if selected on different channels.