Consider the following scenario:
We have clientside validation, checking if a certain inputfield is valid cf. certain rules and logic. For a better performance and user experience, this logic is in a nanoflow, which is set as an on change on the input field.
Now, on save, we want do this same validation. But the save action is a microflow, so I either have to duplicate my logic, or I have to convert my on change nanoflow to a microflow. Both options are not ideal.
So basically, I think when creating logic in a sub flow, it shoudn't really matter whether it is a nanoflow or microflow, it is generic logic which I should be able to call from either a microflow or nanoflow.
This could be achieved by adding a Rules processor to the client side runtime, that way you can use Rules as a way to set up the validation and then use that in your nanoflow and your microflow.