Pretty sure Greg said something along the lines of not wanting to add more content to GT6 and that as a whole the project has been more or less completed. I don’t think he will retract on that in the future, so don’t expect him to do anything but bugfixes/edits/mod compat, even by 2024 
That aside, if you want more stuff to play with, just do it yourself. The GT6U guys did their fork. On a basic level you could do absolutely anything you listed with scripts even without any coding knowledge, if you knew what you were doing. The new horizons team wrote mods, forks, scripts to make the pack exactly what they wanted. Take a page from their book.
Greg has given you the means. It’s up to you to use the tools now.