So far I'm unaware of any scenario on bananas that use a game script other than the basic tutorial. Perhaps one of the problems is that scenario authors and Game Script authors tend to not be the same group of people? The Game Script authors are perhaps clever enough to write what they want generic enough that it works on any map and doesn't need a scenario.
So, perhaps if *someone* makes a Game Script that allows some simple dynamics to be added to scenarios by binding the scenario to this Scenario toolbox GS and configure it to execute some actions at given dates.
For example if a scenario author put the sign "Ind 2, 1978" at a tile in the scenario editor, that could be a message to the Scenario toolbox GS to build industry type 2 at this tile in 1978. There could be a additional flag to tell what logic it will employ if the tile is occupied at 1978. Of course the GS will remove all these command signs at the start up of a new game.
As I have not been into thinking about what scenarios to make, my ideas are probably limited to a subset of what is possible and is useful to scenario authors. It may not just be limited to building a specific industry at some location a given year. There could be lots of other things.
What do you think about these ideas? Would you use a GS like this for your scenario if it was available? Are there any fundamental things that you would like to be able to declare to the GS to do. Or is it just a useless idea?

Let me last add that I'm not sure that I will invest the time to create something like this. The idea just came by my mind.

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My OpenTTD contributions (AIs, Game Scripts, patches, OpenTTD Auto Updater, and some sprites)
Junctioneer (a traffic intersection simulator)