If the problem is that people dislike tediously managing a lot of cities, the solution to that problem is not to address the "a lot of cities" part, but the "tediously managing" part. As interesting as it might be to think that a small and focused empire can compete with a large, sprawling one, the problem is that in practice, creating a small and focused empire is easy and boring, while creating and maintaining a large and sprawling empire is challenging. It's most obvious when playing the types of offshore expansion maps that a lot of people love: what is the point of founding new cities halfway across the globe when your current, 4-city empire is a lot better off just staying as a 4-city empire? Why go the extra mile of making a larger empire when your current, smaller one will do you just as fine? If people dislike how tedious it is to micromanage citizens in every single city all the time, writing better citizen automation code is the solution. If people dislike having to keep track of what buildings they need to build in which cities, introducing and having a reliable production automation system is the solution (think Civ5 puppets, but actually smart). If people have difficulty passing a college course, you give them more options that help them achieve a passing grade, you do not artificially lower the course's difficulty to high school level to let everyone pass...
At the risk of turning this into another one of the usual Civ5 design analysis threads, I believe that in its current form, the idea of wide vs. tall is flawed, both from a historical standpoint and from a gameplay standpoint. There is no reason why a large nation could not also have high population density; the choice of spreading out your population vs. concentrating it in a few central areas is a false one. From a gameplay perspective, if small empires can compete with large empires in all of Civ's few arenas of systems, there is no longer a reason to invest into growing your empire beyond its first few cities. In Civ5, people pick Liberty primarily because its challenges make it more fun to play than boring but reliable Tradition: having to juggle gold, happiness, culture, and timing military pushes is a lot more engaging than coasting your way to a peaceful, 4-city Tradition Space Victory or an Information Era Domination Victory. Civ4 might not have balanced tall vs. wide, but that's because it was never really an aim: small empires were not rewarded because expanding into a larger empire was a lot more challenging than just sitting in your corner of the world, trying to spam wonders, and obviously people should be rewarded for challenging play.
If the goal is to let people who play small empires remain relevant, than one of two things should be done: either small empires need to be presented with the types and magnitudes of challenges as those that are faced by people trying to create and maintain larger empires, or small empires must only be given incomparable advantages over large empires to balance out the numerical rewards of large empires. Let me give you a simple example of one possible incomparable advantage: a small-exclusive, empire-wide bonus (via civic, policy, etc.) that gives two free military promotions to all units. Small empires might be able to produce less units than large empires, but the units they produce will start with two extra promotions, and it is rarely clear whether or not the extra promotions are stronger than a numerical advantage (8 crossbowmen with Barrage II or 4 crossbowmen with Barrage III and Range?). Other examples might include: restrictions to flexibility (eg. in a Civ4 system, more cities would generate more anarchy when civics are changed), restrictions to choice that do not force players to flatout inferior choices (eg. in a Civ5 system, wide players would not be able to open as many policy branches, though vital branches like Rationalism would always be available), restrictions to diplomatic options (eg. in a Civ5 system, city-state influence would be much easier to acquire and maintain as a small empire than as a large one), etc. The key point is that the benefits given to small empires must not directly convert to the numerical bonuses that people would associate with large empires: you cannot compare proposed small advantages like being able to switch civics quickly or generally having more votes favor your proposals in World Congress to wide advantages like having more production or having more population, and that's ultimately how an ideal small vs. wide system would be designed.
This skewness is inferior to the way Civ4 was geared toward rewarding big empires.
