I am hopeful for some more QOL changes, here are some examples of things that i would love to see:
minor characters need to create offspring too, its kinda useless to have the iulian family in rome when they die out within one generation anyways. also i want more historical characters, like famous leaders/philosophs/rulers to appear by event, just like archimedes of syracuse does. i think the characters aspect of the game is very fun and should be expanded, it's always nice to build a career for a character and having him/her achieve great things. this is ofc even better if that character is of historical significance irl, for example pyrrhus or the diadochi.
also we need more women, and maybe dont make AI women instantly married as soon as they turn 18? more often than not there is literally not a single woman in my realm that i am able to marry, sometimes i dont want to marry a foreign princess....
one personal thing that really annoys me about all the PDX games that i played, is the apparent irrelevance of straits/canals. if i control both sides of the bosporus, or if i fully control egypt including the pharaohs channel, rome shouldnt be able to conquer arabia or crimea. they literally dont have any way to access it?? straits/canals should have a toggle, that allows the controlling nation to block passage through the strait for any hostile nation and MAYBE allow trading partners to pass.
Edit: also i obviously want more flavor, but these are the actual mechanical changes that i want to see