Battle Hardened (+30 HP for palace guard) is one of the reasons why palace guard is good and annoying in imperial. I think if the tech is instead providing HP buff to spear instead of the palace guard it would fix the balance a little by having the inferior landmark, imperial palace, be able to unlock the skill in castle age. This could nerf china imperial a little bit while buffing china mid game against knight (which I think is china’s weakness according to the Stat).