Trade embargos are completely usless to players, who hardly make trades and are hardly an annoyance at all when emplaced by AI(do they even do this?).
So to make trade embargos a more effective weapon - just like they were in real life- and keep it simple and intuitive, I think they should cause a very small morale penalty, to a small maximum (Ei. -1 one morale for each country that has embargoed you, to a maximum of 5). This would be just like how being at war affects your morale, however with a much smaller effect. When war is declared with a nation you have embargoed, the trade embargo morale penalty is removed and replaced with the war one. This morale penalty would be added to the current trade embargo system of preventing market trades between embargoed countries.
I think this is an effective and simple way of revamping the current trade embargo system, and hope you do as well.
So to make trade embargos a more effective weapon - just like they were in real life- and keep it simple and intuitive, I think they should cause a very small morale penalty, to a small maximum (Ei. -1 one morale for each country that has embargoed you, to a maximum of 5). This would be just like how being at war affects your morale, however with a much smaller effect. When war is declared with a nation you have embargoed, the trade embargo morale penalty is removed and replaced with the war one. This morale penalty would be added to the current trade embargo system of preventing market trades between embargoed countries.
I think this is an effective and simple way of revamping the current trade embargo system, and hope you do as well.