The real question will be what are you going to do with all this information? The flight plan is prepared a couple hours before departure with the expected weights. The orders go out to the fuelers to put X fuel on plane Y at stand Z. The last thing we get from the ground staff is the load sheet. We compare the actual to the planned payload and as long as the actual is less, we're good to go.
So you weigh people as they check in and wouldn't have your payload till 30 minutes before departure. Then prepare the flight plan, get the paperwork to the crew and get the fueler to show up at the plane. At most large airports there is no where near a fueler per plane so you wait. About the only way to make it work would be to close the flight a couple hours before departure. For what? We figure it costs 5% of the tankered fuel to carry it. Say you have 300 kilos more than you need. That's 285 kilos you won't pump at the next station. We're talking about 5 gallons. Most fuelers squirt that much extra on all the time.