Actually I don't like this strategy, and expect it can be fixed somehow.

First introduce some concepts:

1.Global yields and local yields

Global yields means it is provided by one city, but its effect is enjoyed by the whole nation, like money and science.

Local yields means it is provided by one city , and its effect is mainly enjoyed by this city only, like food and industry.

So one city must provide some food and industry to function properly, while it doesn't matter even if one city provides no money and science at all.

2.Tall strategy and wide strategy

Tall strategy means to raise the efficacy, like science per district/population/tile. In humankind there are infrastructures, legacy traits and emblematic quarters.

Wide strategy means to raise the quantity.  In humankind we can build more research quarters, or appoint more researchers to yield more science.

It's best to be both tall and wide to gain more, but we need to give some limitation for both of them to balance the game. 

For tall strategy, infrastructure can be built only once per city, legacy traits can't be duplicated, thus limiting the whole efficacy. But emblematic quarters are an exception, they can be built once per territory, so a city with many territory may have a huge bonus in efficacy.

For wide strategy, the number of researchers is limited by the number of research quarters, and we need more and more industry to build more and more research quarters in one city. But we can gain more research quarters simply by attach a territory with many RQ to it.

So this is the strategy:

1.Choose a central city, build every science related infrastructure, and a few RQ if you want.

2.Other citys build a cluster of RQ, with EQ that can raise the efficacy(like Joseon, French, Swedes), in a territory you want to DETACH LATER!

3.Detach the territory and attach it to the central city, with Inherited Land civic, it won't cost much.

4.Build a cluster of RQ, with EQ in another territory you want to detach, then continue the process.

Then you will get one city both tall and wide in science, with others yield no science at all.