Heyho,
Me again 
During flight school I always accounted for the empty tank in the W&B (weight and balance) calculation.
Maybe one could also include this and a third point in the W&B?
The weight at takeoff is already in the table.
Let’s call it point T (for TO)
We also know how long the route is planned to be. With the specified consumption you can enter point L (for LDG).
And it’s also known what the total amount of fuel on board is. Setting that to 0 then gives point E (for Empty).
That way you have the takeoff mass, the planned landing mass and the mass if the tank is empty and can see that everything is OK.
Or is that too much? 