Straight to the case: it takes more than 2 minutes to manage your populations and sell goods past 70th turn. The reason would be increasing amount of races you are encountering as well as unlocking new types of tradable goods. It's just a half of the turn's routine wasted on the most grindy actions.

Cooldown can help with that. For singleplayer that would mean more reward for planning ahead, and for multiplayer that would be faster turns.

Of course, some underdog nations can keep no CD on these actions. Vaulters, for example, can and should be nerfed with it. Not for personal, but for balance purposes :)

It does depend on the size of things, but I get where you are coming from. The micro on aynthing over 1v1 tiny can be and is usually overwhelming and AI management underwhelming.

But you can always force timer on MP and make players choose.

In SP you can get away with ignoring the pop mechanic movement altogether (but it IS nice).

How do you suppose a trade cooldown would work?

Do i get to make a single trade transaction per turn? Or do i get to make transaction one turn in 10?