Coria was the aggressor in this war, and made a rather ludicrous and unprovoked demand.
I don't even know where to start with that comment. Do you even know why the war was started? There were two main reasons, but both were due to the actions of the Estonian government.
Firstly, and the main reason Saeculo proposed war, was because of their handling of the Herunumen incident. It's funny, because as a player, I suspect that it was a member of an allied realm which originally put the bounty on Saeculo's head for his support of Eston! How ironic is that? In the League of the Eagle, Saeculo had been quite outspoken in his support of Eston and then suddenly found himself with his first and only bounty, putting two and two together, I'd suspect it was an ally who placed the Gold on the bounty board.
Regardless of this, and despite the protection Coria had offered Eston (preventing access of Carelia to through our lands) Eston allowed Herunumen to escape, the very man who had stabbed a loyal friend of Eston's. Now I understand that many in Eston won't know that Saeculo was pro-Eston, but nevertheless, Saeculo felt betrayed by those he once considered friends. If you remember, Coria did not participate in the CE/BoM war and the reason for this was because Eston was involved and we didn't want to attack their troops.
The second major incident was when Talerium assassins assaulted an Estonian. Because of this, we were threatened and the trade which once existed was halted. Regulus has used the same argument against Coria, but I really don't understand how people can justify attempting to punish Coria because of the actions of an ally. Those nobles did not traverse Corian lands to reach Eston, nor did they have our support, we didn't even know until after the fact. Yet on both occasions with Eston and Hammarsett, this has been used as an excuse to punish Coria. Both instances, it's ended in War. Lesson? Be just in your punishments and don't punish those un-involved.
Friendship between Coria and Eston had been growing before this war, since the foundation of Coria in fact, and but for those two occasions we wouldn't be at War.
Indeed, I believe the player of Roland can confirm that Saeculo was willing to travel to Eston to speak with their King over the matter. Coria actually tried to avoid war at first, but then King Jean demanded that Saeculo leave Eston for "his protection could no longer be guaranteed".
But as you seem to know, can you please tell me what Coria's demands were? Originally, it was that their Judge, Athena be punished and removed from her position. Funnily enough, your own rulers demanded the exact same thing in regards to Roland and Jean before they would help out Eston.
Then during the war, the reparations we requested was for a food producing region in compensation so that we would not have to depend on Eston for food in the future and so that they could not attempt to use this as leverage again. Thus our peace demands were not harsh against Eston when we had the upper-hand, and Eston's were not harsh against Coria when they had the upper hand, so I fail to see your point?
Now we are at peace again, Kerwin and Saeculo seem to get along, and I wouldn't be surprised if both realms start strengthening their friendship once again whilst respecting their current alliances and commitments.
Additionally, it's the choice of your own rulers to go through the Corian mountains. Other than flying (this was not an available option in the Medieval period) or going through Talerium, how else do you wish to gain access to the CE?