Just a random idea to use hooks on signal, based on data from stations and industrie
Hooks will be provided by a "hook signal" button in the interface. After clicking it, the user may select a tile that is covered with tracks. If no signals is available on that tile, the signal will be created, a controllerbox may show up to make it clear the tile has logics. When clicking on a track with a hooked signal, a window will pop up to set up some settings (amount of cargo before trigger for example) and an option to remove the hook.