If you could include new mechanics, features or functions in AOE-3, what would you implement?

I am aware that it would be very difficult to implement. That is why I was not able to propose how.

For the treated mode most of all it would be good.

This without replacing the current mode. We would have 2 ways to trade.

As in AOE-4, being able to choose the biome?

I have also thought about cattle:

At least extend the limit a bit.

It is a pretty useless building. Maybe you can build a wall in a linear way, and only include the pillars in the corners.