Is the sea gate castle and trade bags too OP?

The 40% extra gold from trade along with the 40% movement speed buff is notoriously high amount of boost for trade than any other civs. The effect is lingered for 15 seconds making it enough for one castle to cover more than half of the map in 1v1. The +10 armor buff along with its 40% movement speed make it very tanky and can get away easily from raiding. Hence, I think maybe the armor buff could be tuning down a bit by having +3 to +5 armor. The trade bag could scale with age as well (-/ 20%/ 30%/ 40%).

In exchange to the nerf maybe the underwhelming landmarks like Sultanhani Trade Network could receive a buff like generating more gold per min or 10% extra gold when traders drop gold at this Landmark.