Hi @angelo_mekenkamp ,
Thank you for taking the time to share your feedback. The suggestions you have made are valid, and are something that we will strive to provide, but given the tight deadline to deprecate the non-public endpoints, most of our focus and effort is on publishing appropriate v3 endpoints to replace them. The sooner we get them published, the more time our users will have to migrate.
To keep the communications focused, we initially decided not to post the full list of non-public APIs we intend to deprecate without a replacement ready to go. However, I can work on getting a full list of non-public APIs to better prepare users.
Deprecation headers are something we plan to make standard for our V3 APIs for the exact reason you mentioned. However, it is not something we have planned for our non-public APIs. This would detract from the effort to provide the v3 APIs. Please subscribe to the API deprecations category to get notified when new endpoints are deprecated.