Too busy to catch up in full, so analysis, vote, then amble up the thread in my spare time:
[ ] The High King could make it so
Karaz A Karak - This is sensible, the Karaz Ankor is stabilizing, don't rock the boat.
Karak Eight Peaks - This is Thorgrim shutting down other holds successes again.
Holds along the canal - You're telling dwarves, to stop a major investment, which has already started earthmoving. Thorgrim is either going to need to pay out the nose or lean on their oaths to the High King.
Empire - Oh good, no need to be inconvenienced.
EIC - Had just spent the last few years pivoting to take advantage of it. Terrible losses expected.
Marienburg - Victory!
[ ] For sufficient concessions
As above, but Thorgrim could bribe the Holds into line instead of forcing them, except Belegar would get even more sour over it.
[ ] They can make up for the loss in trade
Karaz A Karak - Has to pay for the actions of their nominal vassals. May be somewhat grumpy, but the Karaz Ankor does not lack for material wealth.
Karak Eight Peaks - Has to pay for the actions of our allies. Fortunately money is one thing Karak Eight Peaks has no lack of.
Holds along the canal - If your project causes unintended harm to your allies then you pay compensation. Perfectly reasonable.
Empire - Things will be shaky for a few years, but not dangerous.
EIC - Makes mad bank enabling the new trade along routes they've already seized control of.
Marienburg - Worst case scenario. Ulthuan will not back them in an offensive war, a trade embargo will spur their internal unrest(remember, trade embargoes are operated by the merchants making money off them), and if they go assault Ironclads on their own Ulthuan will shrug and let them die.
[ ] No, but they could help break the blockade
Karaz A Karak - May not actually be involved.
Karak Eight Peaks - Remember those dumbasses running banditry around the area. Yeah, this is just more bandit busting. Sensible.
Holds along the canal - Somebody is attacking an ally for something we did? Grab my ironclads!
Empire - If it works, great, if it doesn't work we've got a shitshow.
EIC - Not really affected
Marienburg - They can try to call in Ulthuan, it may or may not work. It'd definitely give their ruling council a lot more popular support, nothing like a war to inspire people to double down on their decisions.
[ ] No, but they would fight beside you
Karaz A Karak - The oaths of alliance with Sigmar's alliance involve defensive wars. There is no actual obligation to suicide pact into Imperial bad decisions. Assaulting Marienburg over miles of bad terrain is expensive in blood and money. Pass.
Karak Eight Peaks - Marienburg's been annoying Eight Peaks a little over the canal sabotage. This would be a cointoss, I can't say which way Belegar would jump, because reclaiming Marienburg might or might not push the right buttons.
Holds along the canal - Marienburg's already been attacking them, punching back is nice
Empire - RECONQUISTA! WAAAGH!
EIC - War is briefly good for business, then very bad for business.
Marienburg - They can almost certainly call in Ulthuan assistance for this. See who blinks first in the game of chicken.
[ ] No, they cannot be dissuaded
[ ] I don't know
Empire - The Empire wouldn't just accept "deal with it". They'd do something else unexpected when strategic goods dry up.
[X] They can make up for the loss in trade
Play the game of hearts and minds. Marienburg's embargo is fundamentally a bluff, far too many of their own merchants rely upon the imperial trade, and they'd be taking massive losses on a monthly basis, coming to a head in a half year period as reserves run out, goods start to spoil and the smaller traders will be looking at opportunities to rise with the change in the trade winds.
If we do this option then Marienburg's options are:
-Hope the Empire or the Karaz Ankor gets entangled into some war or another before their domestic pressures grow too great.
--They can help this along with their agents trying to spark civil war, but if caught...well you know whats the fastest way to solve the Nordland/Middenland spat? Have proof a third party was egging them on to their mutual detriment.
-Find alternative trade partners...in a region where more than half their biggest trade partners are Imperial or Karaz Ankor.
-Assault the Canal directly or indirectly.
-Assault the Empire directly or indirectly.
The Karaz Ankor can't afford lives, but gold, and goods? They have those aplenty.
(It'd also be really hilarious if Marienburg embargoes the oceanic silk trade just in time for Karak Eight Peaks to launch a new line of silk products)