I love the user controlled job orders, are there flaws in this system? Of course.
I believe it would be better to stimulate the economy a little bit, f.i. now you can eat from one burger and one bottle of water and you satisfied that need for a couple of days. If you would need to eat and drink more to satisfy the needs there will automatically be more orders.
Adding a maximum amount that you can order at one time would increase the numbers of jobs. I mean it makes no sense to order something like 200000 liters of fuel as that means around 200 tons of load, while a truck can carry a max amount of 40-60 tons? Same for foods etc... the space in a trailer is just not unlimited as it is now.I understand that it maybe is hard to implement this script wise, but we are all here for RP so please shop owners when making an order use your common sense and try to get the requested amounts in one job realistic.
I also notice that whenever you have done a job and return your vehicle you don't need to refuel before returning the vehicle. As such a lot of the fuel sales is missed, every sale that could have been and doesn't go through is less orders for the truckers.
Just my 2 cents