Even with centralized loading there is still a lot of work done at the local level: verification of final positioning of ULDs, special load info for bulk compartment, ULD volumes/weights, final fuel, fuel density, runway in use, etc. The local ops agent is able to update the information and, once it is all confirmed, "validate" the data which advises the central load staff they can proceed to prepare the final loadsheet. Once it is prepared it is dispatched back to the station via telex and/or to the aircraft by ACARS. Keep in mind most of the info is updated bit by bit throughout the hours leading up to the departure so the load planner can work little by little as info is input, awaiting only the final details and confirmation to put the loadsheet together.
In the event of a change in the number of passengers after issuance of the final loadsheet (e.g., no-show passengers), we can print an LMC locally as long as the maximum number of passengers+baggage added/subtracted is 4 or less. Any other changes, like offloading of a pallet, change to hold positions, etc. require a new validation of the load data and resending of the loadsheet by telex.
It works very well most of the time although many traditional ops agents have trouble to give up control at the local level.