Pipeliner

Add a stable API and those users with the expertise (and a burning desire to so so!) can develop new bindings beyond the obvious candidates for interpreted languages (Javascript or Typescript; Python). Personally I'd like to see something for compiled languages too (C++, Rust) but my skills aren't up creating a binding.
Although I've echoed some preferences myself, I still don't think saying "It must be language x or language y" is the way. Better to set things up from the outset so that other bindings are possible later on.
Speed of execution isn't so much of a thing from where I sit -- much likelier to build a complex single page table setup than a 1500-page behemoth these days! For my uses, speed of development wins over execution speed nearly all the time. That's why I'd love to see Python. But I could live with Javascript/Typescript with only limited grumbles

I think scripting support would be a wonderful feature. I would love a good documented API, maybe even a well done scripting environment (persona?) with an included library/documentation.
As of languages I would prefer something fast to write and easy to read like python, maybe even something eloquent like ruby. Javascript has a hideous code structure (things like }); are completely normal), though there are also many pros for JS. 
But maybe think about making scripting more accessible for the average user. There definitely are ways of doing this, if one is willing to go there. Drag and dropable scripting may be possible, or even node-based programming like NodeBox. 
Well, this should of course not replace normal scripting, but extend it and let more users be able to use the capabilities of scripting. 

I only work with Python for automations. It can be slow sometimes but is easy to laern for beginners. Hope there will be the possibility to script with Python someday

To be more precise. It is example how can you scripted Affinity Publisher today. It is not easy and comfortable solution. First you have to use this aproach to create more user friendly library. AutoIt I put here as temporary solution before full scripting will be implemented.
Personaly I prefer Python for short and robust code. I dislike JS as sometimes not clear for me.