Seconded. Considering that ruler's keeps and military garrisons in medieval Europe typically maintained arsenals with which to forge, store repair arms and armor for their soldiers and guards, a smithy should be the bare minimum for outfitting the Boyar Guards. A woodworking station for outfitting archers and shieldbearers--and perhaps even a tannery for crafting and maintaining the guards' boots, belts and jerkins--would complement a better equiped standing contingent.
Though they may not be deemed as necessary as the three previous crafting stations, herbalist stations (for brewing healing tonics and making poultices) and alchemy stations (for fabricating anything from lamp oil to waterproofing tars to siege-breaking Greek fire) certainly couldn't hurt the self-sufficiency of the Von Zeklos keep, either.