The Issue:

When independent people turn their outpost into a city it typically has zero population. The army then usually patrols the territory the city is located on but often is not inside the city which means you can steal the city with even a single scout for free. The independent people then go into decline and waste away without even trying to retake their city. I use this to get a free city or two in the early game pretty much every run right now and don't think it should be that easy.

Possible Fixes:

1. Make the independent people army in charge of protecting the territory stay inside the city at all times. I like this fix the most because it will still be possible to get early game cities but you will actually need a small army instead of a single scout.

2. Make independent people cities start with 1 pop always. I don't like this fix as much because it will still be pretty easy to beat them in ancient era before reinforcements unlock.

3. Make the independent people try to retake their city when going into decline. This one probably would be difficult to implement and I like the first option better but wanted to include it.