There have been a couple of people on RCS asking for something like this, but this would be the most appropriate one I think:
Some kind of fall off system. This gif shows a widget being used for that, but I don’t know how we would seamlessly incorporate that into blender, as I don’t know modo at all, and am not sure at what step in the bevel process that the widget should show up. I suppose if we wanted to take that route it could be a tick box in the operator pop up box, and in the modifier. If ticked, then a widget appears.
Widget or not, I agree that I like the idea of having the bevel weights not being an “on/off” switch. If they correspond more to a 0-1 float range, then we could have excellent control. It might not be the speediest method in practice, but it sure would be flexible.
I would image in the future if we had a vertex group node, we could randomly assign bevel values to different vertices, and get some pretty wild results!