Discussed plenty of times already on the forum, and it's surely on the list of the upcoming updates.
But first we'll finish the scenery editor (with the ability to position marshallers and docking systems in any scenery) and do an interactive graphical Airplane editor, they are more important because will allow users to perfectly adapt GSX to any scenery or any airplane.
After both editors will be complete, we'll work on new discussed services, mainly lavatory/cleaning and de-icing.