From my experience with the Cooper zwave scene controller, in general the devices do not really fit the ST model. ST would prefer that all sensors (a button controller) communicate to the hub and then the hub commands the actuators (relays and dimmers). In the zwave world devices like a scene controller are designed to communicate directly with the actuators, by passing the hub. When I wrote the DH for the Cooper scene controller I did my best to make both things possible. However, when you hold a button on the controller there is no information sent to the hub to tell it which button is being held. It is only told that a button is being held. This is because the device is designed to send the held information directly to other zwave devices it is controlling. I think this is why ST has not jumped on making these devices run local.
I use my Cooper controllers daily and they work very well. For the most part I use them as intended by the designers to control other zwave devices directly. The one big advantage I see to this is, I can unplug and disconnect my ST hub and the controllers still control those lights.
Turn on the hub and I can make switches act like three way switches that aren’t and tell Google “Good Night” and have all the lights go out. Excellent added functionality.
This big limit is: I cannot thru ST control a zigbee dimmer with the Cooper scene controller. I think that puts it out of contention for official ST support.