no way to upgrade or demolish the settlement walls
That's right. There's no way to rebuild/re-upgrade a settlement, so if it's already at its highest level (Large City in TATW) then you're stuck with it.
What you could do is re-enable the ability to upgrade to Huge City. In TATW that was disabled except in one case: Gondor can upgrade East Osgiliath, for the purpose of 'restoring' its broken walls/buildings on the battle map.
You would need to prevent some factions from doing this. e.g. Gondor's will be the East Osgiliath model (on strat and battle maps), Dwarves would be Erebor. Everyone else (I think) would get vanilla M2TW huge city models which wouldn't suit Elves or Orcs, though you wouldn't want Orcs to be able to do it anyway as that defeats the point.
In export_descr_buildings.txt, find this section...
Code:
upgrades
{
huge_stone_wall
}
}
huge_stone_wall city requires factions { gondor, } and hidden_resource osgiliath_east
...and change to...
Code:
upgrades
{
huge_stone_wall requires factions { turks, }
huge_stone_wall requires factions { gondor, } and hidden_resource osgiliath_east
}
}
huge_stone_wall city
That will allow Eriador to upgrade to huge cities, without breaking the Gondor-EastOsgiliath thing.
WARNING: do not upgrade these settlements: Imladris, Edoras, Esgaroth, East Osgiliath. You'll lose their custom models. And you should remove the "huge_stone_wall requires factions { turks, }" if you're playing any other faction, to prevent AI Eriador from doing that.