Content Types in Experience Manager would be one way to create this kind of default content values. This is where you can create one or more Custom Content Types that set default details for new content created in Experience Manager at a given Publication.
If the product were to add these kinds of flexible defaults it'd likely rely on Content Types and the Event System alongside any GUI changes. If going for an extension or automation, I'd recommend, in order:
- Event System to set the values you want based on the Schema, perhaps by copying an existing configuration Component
- GUI Extension to let editors choose from existing content "prototypes," possibly using Content Types settings or again, configuration Components
Functionally, the easiest way to have users set the correct text might be to have them copy and paste an example. For an extension to set such a default, I'd seriously consider some kind of configuration or prototype Component because:
- The default value might change over time
- Other types of default values could be introduced, where users might choose from multiple types
- The default value might differ based on Publication context (and how the prototyped Component is localized)
Finally, you want to set the value on the item's first creation or perhaps only during certain events (creation, copy, and/or localize?). Rather than program this logic into a GUI extension, it makes sense to use the system's already defined events.