Short backstory (sorry that this is a long post)
I love RoM AND, and civics have definitely changed a lot over the years. I know I'm a little late to discuss economic civics changes, but my background is in economics (and some history) and I wanted to provide some suggestions from that perspective. Although this is a game, so playability will trump most else. And I could be completely wrong about what I'm putting forth.
For the early economics civics (currently barter, slavery, coinage, and guilds) I like that "Slavery" is moving to the society category. However, this leaves a large gap between Barter and Coinage. And I don't like the suggestion of "Tribute" being added. It's more of the name, because it doesn't make sense to be placed within the economic category. Tribute is basically the opposite of a subsidy, and might belong in the Foreign Policy category. I don't know the exact effects being planned for it, but maybe it just needs a different name. Either way, no one wants to be stuck with Barter's current penalties.
My main suggestion would be to re add Manorialism (regardless of whether the suggested Tribute is added or not). I am certain that it is a much better fit than Tribute. It would emphasize the rural economy whereas Guilds emphasizes the early urban economies. The name is a tad deceiving because we immediately think of European Feudalism and serfs farming land. There could be a better name, but I see Manorialism applying to large agriculture based economies. It does a fair job with this. Unlike feudalism (which it is tied to) Manorialism is mainly an economic system itself and lasted for many centuries in some areas. So it shouldn't just be relegated to the Feudal Social category civic. It is not just a European phenomenon either. The Shōen system of Japan and the Open Field System during most of the Zhou Dynasty also apply, for example.
Similarly, Coinage doesn't just represent using coins or money. Coinage represents commodity currencies, that is, money with value in itself rather than fiat currencies of paper today. So metal coins, knife money from the State of Yan, and so on. (I think that coinage should have a negative effect related to inflation, but I am unsure about how that would work).
I don't remember what Manorialism had in terms of effects, but here are a few ideas to go from. They would revolve around the farm more or less.
Specific examples for effects:
Side notes:
1. You could change the Barter civic's penalties, but that could change the balance of the game quite a bit.
2. Subsistence was once an economic civic, but Manorialism is similar to that. Pastoralism could be another early suggestion too, but I think it is too minor. I think the Feudal civic should decrease city maintenance a little, but monarchy already does this a lot.
3. Switch Mercantilism's +30% coin from domestic city connections with its -30% coin from foreign city connections, so their bonuses are switched... Coinage has the exact same bonus at 20% and Mercantilism was about exporting so I think it is more accurate to have that change.
In short, tribute doesn't make sense as an economic civic, kind of like slavery being in the economic category. In the line from barter to coinage and guilds, Manorialism fits neatly in early economics compared to tribute. It isn't unique to medieval Europe and represents larger scale farming, and more rural economies in general.