In the end, full of suspicion, Rosemary had made the decision of simply shifting the creation of those weapons to the castle, where they would always be created and assembled under her watch, even if they didn't have the same infrastructure and such already present, she could arrange something, always better than receiving sabotaged goods that would result in poor performances and lives lost trying to operate them.
Those trebuchets and other great weapons were of tremendous importance, before, the undeads had already been an unstoppable tide, within miasma, they held a distinct advantage over the soldiers and other living troops, but now, the darkness was the last nail sealing their coffin, the dead held a potent additional sense within whilst they were completely blind.