I like the idea of having a vassal or two that are more than just something to get cores back and annex. I think being able to pick which idea groups your vassals take would go a long way toward making them more stratically useful.
For example, if you have a march on the border with a rival you could give them defensive ideas. Or perhaps you have a vassal as a conversion machine so you want them to have religious ideas. Maybe you want to have a small vassal that would transfer you their trade power so you want them to have trade ideas. This would go a long way in making vassals even more useful.
For example, if you have a march on the border with a rival you could give them defensive ideas. Or perhaps you have a vassal as a conversion machine so you want them to have religious ideas. Maybe you want to have a small vassal that would transfer you their trade power so you want them to have trade ideas. This would go a long way in making vassals even more useful.