I've added "Touch Speed Rotary 2" to the Rig Exchange.
It is an edit of "CK Rotary" that sounds like the speed of the Leslie automatically changes from slow to fast, with your playing dynamics. No foot switch needed
You can adjust it for your playing dynamics by changing the amount of Ducking in the MOD slot.
If it switches to "fast" with too light of a touch, change the ducking to a lower number (try -4.5 or so)
If it doesn't easily switch to "fast", raise the ducking a little bit ( try -2.7)