The Radial Gauge widget fully supports min/max values as items so no workaround is required. However, widgets are not interested at all in items for min/max values, they are simply interested in absolute min/max values, thus WebIQ notifies the widgets whenever min/max values change, regardless if they are absolute values or originate from an item. Widgets simply don't know about min/max items and they don't have to, because they only need to know the current min/max values.
So if you set item for min/max values on a variable as described before it will work correctly with any widget including the Radial Gauge widget.
However, if you're using a simulation function (like the DSaw internal variable does) this only reads min/max item values once so it won't really work with this. But this is a limitation of the simulation function and has nothing to do with a specific widget.
I will attach a working demo (WebIQ 2.15) that illustrates this working behavior later.