This has been discussed several times and, I'm not entirely sure it would add anything. It's not as if you had to *act* on the fuel truck counter. What you will interact with, will be either Lbs or Kgs or Gallons, depending on your International settings or, in case of a custom fuel control that has its own separate settings, how they are set.
So, what real value or ease of use you would gain by having the fuel counter on the truck displaying in kgs, when you don't have to interact with it ? If you wanted to have an idea how much longer it will take to end the refueling, there's the top green bar, which indicates the progress BOTH in Gallons AND either Lbs or Kgs, depending on the simulator International settings, exactly like the default Fuel panel control.
So, having even the Fuel truck itself supporting multiple units of measure, doesn't really add anything, unless you wanted to check if the counter indication, which is only Gallons, matches the top green line indication which is Gallons / YOUR preferred Unit of measure, and I assure you they do...
