Both positive and negative can be the case.
For a casus belli, you can get positive boni, for no you'll get negative ones.
The marriage event is a good example, which could be expanded.
Change in religion, civics (i know, these are Civ4 examples), settling at the border, culture expansion, etc. could be reasons for war.
These things could be mentioned for some rounds in the foreign advisor, you can choose one or more of these, which result in different boni or mali.
It could really be interesting.
For a casus belli, you can get positive boni, for no you'll get negative ones.
The marriage event is a good example, which could be expanded.
Change in religion, civics (i know, these are Civ4 examples), settling at the border, culture expansion, etc. could be reasons for war.
These things could be mentioned for some rounds in the foreign advisor, you can choose one or more of these, which result in different boni or mali.
It could really be interesting.