Idea Summary
Have a centralized location, e.g., Static Files, where you can reference the Advanced > HTML Template for APEX Email Templates.

Use Case
Some applications have several email templates, and if you have several Apps, you can easily end up with 20+ email templates. If you have a standard corporate email template with custom CSS and need to change it, this becomes a burden. Having a centralized email template to reference would make it much easier.

Preferred Solution (Optional)
Have the ability to reference the template content from files in Application or Workspace Static Files.