I would like a Business Rule to have the ability to call a process Action, Workflow, or Cloud Flow. The use-case is to have a business rule change the behavior of fields on the form depending on calculations or data values from other parts of the system. For example, have the Opportunity "Use system pricing calculation" change depending on the customer selected. Or have a business rule to call an Action to concatenate strings. You could have a Business rule call a flow to create or modify records without having to click the Save button.