It's a very long thread and most aspects have been already said but my 2 cents to add:
I bought Affinity Publisher for occassionall internal usage. To be used as a real live publishing App producing a lot of pages it definitly lacks an API for automation and for replacing/updating parts of the content. Publishing should't be seen as a mouse / human task only. Publishing is in many cases just one channel (of many) for content.
The discussion which language would fit best (JS, TS, Python, AppleScript) has not the same priority as the scope and coverage of that API. AppleScript should be seen as a nice to have since it is locked on MacOS but it shouln't be too much effort to provide additional bindings like JS, Pyhton, AppleScript once there is a robust and more or less complete C++ API. So it is not only a question of Scripting Language choice but also a question of API/SDK and PlugIn-Support.
Since there is no concept for SDK/Integration available by today I'm wondering if there will be (object oriented) Scripting-Support available at all outside the marketing discussion ...