So in summary, there’s no way around it. The commands need to come from the DTH that is currently installed for the physical device.
I can look at adding scene controller and scene activator functionality into my Z-Wave Tweaker (in a similar way that Associations are configured - i.e. one at a time), but will need you to provide some working code examples and explain the workflow in a little more detail. Devices that support Scene Actuator Conf (0x2C) seem to be pretty rare at the moment.