So, I've had a longer thought about our basic battleplan and discovered a decent use for one type of fortifications. Now, the mechanics are a bit open in the air, but if the broadly resemble the previous ones, this will be highly effective.
So, what should our plan actually be? We have gotten an unexpected boon in the form of the strike force we are able to deploy on the other side of the river. This is essentially a surprise attack, on where we aim to destroy the enemy artillery, overrun their rear guard and try to block them from using the bridgehead. This plan potentially enables substantial wins, but it's also somewhat fragile: We need to both ensure that the majority of the enemy crosses the bridge to actually use numerical superiority, deal with the enemy cavalry, and inflict a defeat on the main force in order to surrender, as they would be far more likely to attempt a break out against two units that surrender. It's not unmanageable (potentially killing enemy artillery with our lancers would allow us to start gaining momentum), but it's something that requires very precise timing in addition to masterminding a breaking of the enemy main force on our side while giving the enemy a plausible reason to attempt a bridgehead.
With this in mind, I found a particular mechanical fortification interaction that is extremely helpful: One of the reasons I considered wolf holes to be largely useless is their flat movement cost on one tile, with no guarantee the enemy would actually want to move across this tile. But what if we ensured the enemy would have to move across the tile? To this end, I thin there is a strong advantage to placing wolf holes in front of our infantry. The way this would be playing out is the enemy would desire to charge our infantry behind them, allocate the necessary charge movement (probably a double charge, given the expected distances) and hope to start a melee early. This assault would be happily charging across seemingly open terrain, only to get stopped dead in it's tracks from a wolf hole. Not only that, it would also critically stop one tile away from our units, meaning they would be able to shoot at close range distance (61 casualties from 2 shots using regular units) and loose the impact of their charge due to those getting cancelled (1 action to move into 2 tiles away, 1.5 action to move to the trapped tile in front of them).
The result is an enemy that starts a melee heavily wounded, getting only one attack instead of 2. If combined with the breastworks, we have a forward position that is seemingly best taken by storm and suddenly turns into a heavily fortified position, nearly unable to be straightforwardly charged (3 actions to be charged from a distance of 4, 2 actions to be charged from the vulnerable distance of 2). The relevant fortification is expensive in terms of points (n = length of the wolf holes, 2*n for wolf holes and 2n+2 points if we want to be thorough and protect against charges from strange angels, though that might be unnecessary if we favor a ^ shape akin to the lunettes rather than a straight line). Still, we this as the key element of our defenses, the enemy is dealt an initial blow during contact: After bleeding the units that are crossing the bridge, we then deny them a proper charge onto our forward position, which can't be taken by artillery bombardment (-60 base penalty, akin to Rotholz), a straight charge, only with a slow and extended melee that gives us some firm terrain advantage. The initial assault will likely quickly shatter due to dealing next to no damage and being stuck, giving us an early morale advantage.
The impact on enemy tactics: Rather than a simple assault, the better option is try to bypass the position and hit the vulnerable flanks. This necessitates both a longer line and reserves for a more extensive battle, as you have to keep up the pressure in the center in order to prevent those units from constantly firing and bring reserves in. We can shape the battlefield with this, making the battle center around a longer line at the sides, attempting to flank our main line. From the enemy point of view, this also appears as our core trick: Bloody the enemy crossing force, surprise the enemy in the center and make their assault unviable, and potentially overrun forces with a charge in the center. Against an opponent who doesn't fully commit to the bridgehead, this would be incredibly bloody. Against an opponent that does fully commit, our strike force comes into play and disables the enemy artillery and line of retreat. If we can get some very tight timing right, we can overrun much of the enemy artillery and capture a lot of their infantry.
TLDR: Putting wolfholes before our units basically allows us to prevent a charge on them, creating a situation where we can use 2 reactive shots + melee counter while the enemy just gets one melee attack on their turn. Later units would need to commit to a blind 3 action charge, which will not work in breaking the position. Depending on how far we want to go with this, we could either purely use wolf holes behind naturally defensive terrain or combine wolf holes and breastworks for a terrifying field fortification that can't be stormed, bombarded or effectively taken in melee, only bypassed. Based on the old system, we would get a simply line for 1 fortification action and a quite strong position from 2.
