Make it possible to smith without martial weapons
Both armour and weapon crafting require you to hold a smiths hammer, a martial weapon. Making it impossible to do either if you lack the feat. I surgest smithing hammers are made a simple weapon, possibly using some kind of mace based model to make it easier to do both crafts.
While I agree with not needing martial weapons, why simple weapons? Monks, Rogues, and Wizards don't get Weapon Proficiency (Simple) so they'd have to still use a feat. Druids don't even have access to take this without multiclassing but that's more a thematic thing and I don't see a lot of Druids being interested in smithing.
If we go this route is should be based on a club. Everyone can use a club.
Added Smith's Mallett v6680