It would be valuable to be able to create and modify dashboard widgets via the API. Currently the only way to bulk update content is via control center, and that still creates copies of the dashboard from the template set.
With API access users could point to specific formatting options, as well as leverage information from other services to create/customize the visuals on dashboards. Examples of these could be to pull company logos or color codes to automatically customize a layout to that client. Or the ability to change data sources, graphical layouts, or embedded content dynamically.