I'm a fan of playing tall as well, and unfortunately, it is not viable at all in Civ 6. I understand those who complain that Civ 5 was balanced too far in the opposite direction, although I don't think it is quite as strict as some say. In my normal, peaceful Civ 5 game, I would typically found 5-7 cities, and do extremely well with that. In Civ 6, you need a lot of cities to be competitive, because no matter how tall you make your city, you are not going to get that much more out of it. Yields are largely tied to districts, and a district in a small city is worth just as much as a district in a huge one. Buildings typically give flat yields, rather than percentage boosts like in Civ 5. District workers give you very little, and getting great people is tied to buildings now, rather than to specialists. You will always be better off getting a bunch of small cities, rather than trying to make a smaller number of large ones. There is a sort of pacing mechanic in form of a somewhat dramatic escalation of production costs, but it cancelled out by chopping and gold purchasing, which is how you generally build stuff in the late game. More cities -> more stuff to chop. Also, more cities -> more trade routes -> more gold.
I actually didn't mind global happiness in Civ 5. It provided a pacing mechanic, and meant you had to acquire more stuff, in the form of buildings, resources, techs, wonders or city state friendships, in order to keep a larger (in either the wide or tall direction) empire together effectively. It also tied into the ideologies system in the late game, and helped make the ideological war more interesting. Typically you would work to make your ideology influential, to make competitor civilizations more unhappy, and force them to convert, which would loose them a bunch of tenets. However, each ideology also offered means to combat unhappiness in the form of tenets or wonders. It gave me something to focus on in the late game, which I found much more interesting than setting a dozen unimportant production and worker orders per turn.
I don't expect them to make Civ 6 as biased towards tall play as Civ 5, but I really hope they will at least make it somewhat viable. At the very least, they need to make large cities a lot better, including making them produce more great person points. Making a size 24 city takes a lot more effort than making 6 size 4s, and should be better, not vastly inferior as it is now. Also, it makes absolutely no sense that a Commercial Hub in a size 4 city should be producing as much gold and great merchant points as the Commercial Hub in the worlds largest metropolis.
I have gone back to Civ 5 for the time being.
