Civ with all blacksmith techs an age earlier

How strong would it be for a civ to get every blacksmith tech one age earlier, and be able to build blacksmiths in Dark Age? What else would be needed in order to balance that, e.g. missing techs/upgrades to compensate?

It seems very strong, but they would still face the same issue as old Burgundians - e.g. a feudal age eco can’t easily afford castle age techs as costs ramp up. Getting e.g. bodkin in Feudal would be huge for archer rushes, galleys, towers; but also slow down your castle time by 200f100g. It puts pressure on enemies to also go Imp earlier than they might, to keep up with techs (although one could also not give them good imperial techs to make that less oppressive). Could also make for interesting all-in drushes!