Another suggestion -- it would also be nice to have a user-defined fan-speed function a-la MSI Afterburner (i.e. table of temperatures v.s. desired speeds).
I've given this a bit of thought and realized that this is pretty straightforward to do with an external script or driver. The driver can query the core temperature via the clocktweak interface, parse the JSON results, and then set the temperature accordingly.
Unfortunately I don't have a card that allows fan control via clocktweak. I'll likely be getting one soon and will post this script when tested.