Are there any plans for repaints and configuration on the fuel truck like your other vehicles?
There are plans to improve refueling in general, much more than just repaints. No timeline at the moment.
This would allow WFS stairs to come to Federal Express aircraft rather than some random selection.
As explained several times, it should be the airline code of the *parking* that affects the selection of the service vehicles, not the airline code of the airplane, because it would otherwise lead to unrealistic situations, like an airplane flying internationally, that gets serviced by vehicles from his own country when in a foreign airport, instead of the local services, as it should be.
And, the selection is not random, is based on a scoring system (explained a bit in the manual, and in a more detailed way in the PaintKit), with random selection happening ONLY if the score is a tie.
Which means, to obtain what you want to achieve, you should ensure your AFCAD has the parking codes of the handling company for the parking spot you use.