i think, it will be good if after a war is over the winner has some options like-
-- Loot( the usual thing, like the winner gets loser's resources)
-- Disband Military( it would reduce all military units(except spies, missiles& nukes) by -30% and cost of building new units +10% for next 5 days)( though the losing nation gets more days in beige)( not available during raids)
-- Sack Cities( heavy infra penalty in all cities and infra cost +5% for next 5 days)
-- War Reparations( Winner gets 25% of losers net monetary revenue for 5 days and any grants from the alliance bank are not possible for the next 5 days) ( not available during raids)
I think this will make war endings more dynamic and losing wars will have a long term effect.