Okay. I will try to look at the plan and see what are its main strengths and weaknesses, and how to best use them or get around them respectively.
The first strenght is that it does not require much in a way of getting approval of the other Lords. The plan is hard to argue against. Why would you disagree with relieving Stoneheim immediately and choose to leave its fate up to chance? And if Reinhard decides that the Royal army will go along with it, what choice do the rest of them have? To stay behind and walk there on foot? That would be no better than deserting and walking back to Myrgard, because by the time they reach the city the battle would be already over.
So it should avoid one of Reinhard's main concerns:
Getting Lords Berg and Seinsheim to cooperate though may take more time than we have.
We can start gathering the Royal forces and
checking 'preparing' them right away while the Prince gets the Lords up to speed so that their guards could follow suit.
Preferrably, we should be done with this part by the time Mazzarin wakes up and asks us WTF is going on, because the Mage knows better than anyone that you don't need any special insulation from 'harmful influences' to use the Gate. If not, then, hopefully, Reinhard can either stall him until we are done (he has no idea of our plan yet) or explain why we are taking that extra step without him alerting the whole camp. Alternatively, we could inform him through Emrys.
To do everything quickly we will need to enlist the help of Finn's host, and to find Finn we should free Cropper first.
We should know who is who in the army by the time the Gate opens.
So far I see the option to deal with the traitors outside of the view of the main army is the preferred one. Alright.
We should ask Reinhard if there is a location in Stoneheim that is big enough to hold the entire army, and that is easy to secure and defend, and removed far enough from the conflict raging there that it has a reasonable chance to stay in one piece. The Gate should open there, drawing from his/Finn's/Mazzarin's memory of the place, similarly with how it was with Eris.
One question we need to decide is if Maz should stay on our side of the portal, or go in once he is done casting the spell and tranfers it to the Seekers. Things are going to be much more orderly wherever he stays, as he has the power to quell any potential unrest and I doubt anyone in the army would openly oppose him after the Sea of Glass.
I think we should send Finn's people and our mercs under Berty on the other side, along with a considerable amount of loyalist forces with someone who is both uncompromised and commands a lot of authority (probably General Kjell, if he proves to be loyal). The General should be made aware of who the subversives are so that he could deal with them accordingly.
We also need to make it clear that we belong to the Royal army, lest the city defenders try to kill us.
Our mercs should go in fully armed (explosives included), which we could explain away with them being specifically trained for Gating warfare, while the others should be separated from the explosives under one pretext or the other. The grenades and other ammunition will be handed to them upon arrival. Naturally, those crates should be protected almost as heavily as the Gate itself.
The explosives should only be trusted to the ones loyal to the cause. The subversives should be disarmed (if they weren't already) and subdued somewhere where the main army can't see it, which should be relatively easy, considering they won't have explosives and will be facing overwhelming odds. The given reason for their apprehension should not be treason - which is, as far as I know, punisheable by death and therefore will force them to resist - but something more innocuous. Maybe their 'Gate insulation' proved to be less effective and they have contracted the 'Void disease' (the symptoms may include higher irritability, lack of respect for authority, and occasionally shouting "I'm perfectly fine, you fucks, give me back my equipment!") and thus have to be quarantined for a day or two until they get treatment. Just a minor setback that will be corrected shortly, meanwhile, please proceed to the
gas chambers infirmary.
Ideally, they should not even become aware of their predicament.
Between the lack of knowledge on the subject and the army discipline where you can't really question your superiors, I believe it will help us handle the matter with the bare minimum of resistance. Nevertheless, we should position our mortars in a way that would allow us to shell any potential troublemakers, just in case. Still, I think even if there would be disagreements, we have Finn's fairies to glamour people into compliance, so I hope it would not come to that.
The Lords, Berg in particular, will require a different approach, but, thankfully, there are only two of them.
We should maintain the numerical/qualitative superiority of loyalists on both sides at all times.
We aren't really required to do anything in particular once the plan gets off the ground, so I guess we can choose to be on whatever side of the gate we feel we can help more. Probably with Finn and the rest of our mercs, helping the General in charge with his task and smoothing things out. That still leaves Maz&Reinhard to run the show on their side of the portal.
Mazzarin will work both as a guarantee of public order, and a safety net in case someone decides to mess with the portal.
Once on the other side, the army will probably need to take a bit of time to restructure, given that there probably will be some commanders who are compromised.
I guess Reinhard will be the one deciding what to do with the 'quarantined' forces. Maybe they can still be used to form suicide squads or something.
So... what do you think? Any glaring weak points that should be addressed?
Also, changing my votes to
BivECCA.