The form processor idea comes from the fact I have been working on CiviMRF (CiviMcRestface) and the fact I have been developing custom api's for clients for data coming from a form on their external website.
Below is a use case at childhood workforce.
Develop a custom api _ Newsletter.signup_ see [https://github.com/CiviCooP/nl.issa.api/blob/master/api/v3/Newsletter/Signup.php] and use that api in the CiviMRF at the Earlychildhoodworkforce.
How would Form End Point Designer fit into this?
There is no need to develop a custom api. The system administrator could create an end point which does exactly this from the user interface and without any knowledge of coding.
Below is the screen of how to edit a form processor
Below an image which represents the architecture with all the components which are out in the eco system.