^I agree it's almost certainly not going to happen, but could you imagine if they made it like Shogun 2 in terms of scale? Rome 2: Italian Peninsula only, all factions are roman families with Identical units. You can play as 3 and the rest are Pre-order exclusives!
I can't wait to get some details though. What features do you want to see carry over/change?
I would like to see the skill trees return, but at the same time I think you should only be able to choose certain skills depending on your actions. It doesn't make sense in Shogun that you can spend the general's entire career defending a castle and still choose attack-based skills.
I also think the food supply system from Shogun 2 Vanilla should be kept,that was a new layer of resource management added to the game and put a lot more emphasis on farms.
Finally, you should be able to retrain troops again! It sucked not being able to retrain your veterans to get the upgraded accuracy/armour in certain provinces