In MoM (and various similiar games) you could see how large a city could grow at a certain location and what resources it would then be able to tap.
Yes, it's a bit more tricky with Elemental cities having varying control zones but that does not automatically make it impossible.
Right now, I have no clue if a city would grow out of it's outposty infancy or not.
When a food resource is right beside it, it's usually a sure thing but most of the time there is none and some cities still grow larger than an outpost. How? Why?
And you can't build additional "food production" because irrigation, which would be required for the city to grow beyond "outpost" and/or tap food resources from further away, requires the city to have grown beyond outpost.
That's why I try hard to hit all new cities with the Bonus Food enchantment. And sometimes that isn't enough.
It doesn't have to be a super complicated visual experience.
Just a "survey mode" which I can use when zoomed in and which overlays the terrain tiles with a number, representing their food production.
If this stayed centered like a 4-6 tile radius ring around the cursor, it would "look" better - like the player was actually "doing" a survey - and it would at the same time allow a rough estimate of the final control zone.