Well, more 'wants' than 'needs', but with scenarios, perhaps you can make a small, popup text panel for editing code if you add scripts. I'm not sure about the actual coding language.
But, I do have an idea. Now, I doubt this would work (I've only heard these questions asked with apps coded in Swift, there isn't much general documentation), but if you wanted some good functional and cosmetic extensibility, see if integrating AppleScript and Windows/Linux's counterparts of that could be possible (you could just integrate the scripts via the right-click context menu or when a specific animation plays).
Would you be able to add touch-based events? For example, play a sound effect or display an animation.