If a player is in conflict with another one, their allies get grievances for not joining. I like it, although it is of little effect, as it makes bounds visible.

I'd like to expand the idea to the “arms deal”.

1. If 2 players are at war,
2. and one of them uses a unit that they built through “arms dealing”,
3. it should create a grievance against the »peaceful« dealer (and have no effect, if they are although fighting).

That's all.

Neat idea.  What would the outcome be for the demand?

• Pay money in remuneration for the attack?
• Break Arms Deal treaty?

I'd go with breaking the deal but I don't really care. Either would be neat, indeed.