I don't understand your point. You would like to know which techniques that minimize work involved in maintaining a codebase / adding features ? It's true that

I don't understand your point. You would like to know which techniques that minimize work involved in maintaining a codebase / adding features ? It's true that it's a topic not very well researched but you also have to take into account others factors (economic, management, incentives, planning etc.). For example, following Conway's law ( https://en.wikipedia.org/wiki/Conway%27s_law https://en.wikipedia.org/wiki/Conway%27s_law ) the software codebase complexity and the way the team is organized are connected. There might be no silver bullet at all (e.g. it's a hard problem involving human coordination)