I don't know if it has been suggested, but would it be nice to link the improve/worsen relations action to a task force in a certain area. So if i want to piss of the french, nothing personal, i would have to park a ship in a sea area with a french presence and generate an event. I'll sail there and through the politics screen select a relations action. It will then generate a message saying something like, "your cruiser tried to sail on a collision course with a french vessel and threaten a ram, relations -10".
Since i'm just an admiral, i figured the main way to show your diplomatic stance is with physical presence of your ships. maybe even let through an event sometimes where there actually was a collison and you lose some crew or even the whole ship.