I also find the latifundium underwhelming. Rome as a civ doesn't have any bonuses to population growth and would be taking Authority, the one early tree with no food bonuses. So it can't really afford to be stuck with two lesser tiles. It has all these little bonuses, but overall works out to be kinda sucky.
Latifundium were also used for livestock production.
The Latifundium were if anything, a negative for culture, as they pushed out the vast rural smallholder class that formed the backbone of the Roman state, in favour of slaves, tenant farmers, and scores sent into the cities.
An idea, but not sure of the feasibility. What if the Latifundium kinda sucks as a tile, but it gives 1+ yield to the capital, scaling by era? Either food, production or gold, depending on the resource. So you would build them in your puppet and conquered cities, to export back to Rome. The UA is the Glory of Rome, but nothing actually makes Rome better as a city than your run of the mill capital, all the benefits go to other cities.
Or it works better in conquered cities, to represent the vast slave or serf populations needed to work them. Of course, Rome did moves, slaves, around.
Something more complex would be a unique resource like the Goth's loot mechanic, for slaves that could be earned basically the same way the Goths gain Loot. If you have enough Slaves, your Latifundium works better. They were after all very efficient at producing goods for export due to the economies of scale and transport, and the enslavement.