I have maxed out my construction tech (LVL 8) in my capital. Yet I can build only 16 buildings in a holding. But there are more than 16 potential buildings in a holding. How to build more than 16 buildings?
You can't build more than 16 buildings. Choices have to be made.
Have a look in common\scripted_triggers\plus_scripted_triggers.txt, 'can_build_more_buildings' and below. Should be easy enough to edit.