That is great. You will be able to use that switch as a way for resetting the controller when necessary.
That is the way the GE Smart Fan Controller works by thresholds to achieve discrete speeds within an analog 0-99 setLevel variable. This zigbee device simply uses binary on-off for each of the speeds independently. Sorry.
You can always try the beta smartapp for 4-Speed Fan Thermostat control if the WebCoRE version becomes too complex. Just look down the page a little to see the info.