These are compilation of feature requests from replies on that thread and from various threads on the forum. Not all of them might be “missing” features but decide for yourself.
Mod support
Existing mods are too shallow and I suppose reason for that is technical unviability of modding the game aka. mod support.
Single player content
We finally got 2 new art of war missions and I think expecting more to come isn’t an ungrateful thing. Same goes for campaigns…