So, plenty of OW could be, and probably IS "I have an army, you have an army. Let's see whose army can crush the other better." Now this is fine, and much of the table top is this, too, so it's fitting, but what about when a Fortification gets worked in? What's a good way to deal with this?
I can easily see using a Basilisk or LRD to blow down the door, but I often feel this game lacking when it comes to incorporating the tanks in with the troops, and they are loud and obvious, compared to troops, too. Would a group of Infantry, kitted out with some of the right stuff, be able to do the deed? Sort of as an advance squad to soften up the structure for a larger force. Using rules from Stronghold Assault, and such, converting some loose Leman Russ Armor and Structure Points into what a wall has seems easy enough. Not sure how well the missile launcher or lascannon would do to fort walls, but it COULD BE fun.
Also wonder what's overkill for an "important" fort's defenses. Certainly, if you make it too cheesy, PCs can't be expected to breach it before getting aced, but I don't know if they would have some heavy weapons on the wall tops (mostly autocannons and heavy bolters for troops, ith a lascannon for the incoming LRD), and maybe a Basilisk inside, at the corner, to IndFire over the wall, onto incoming troops.
Would you let your players just keep fighting other armies on fields, or occasionally make them tackle this sort of obstacle? How might you manage it?