Armoursmith

As i posted earlier the weaponsmith makes attacks stronger/slightly different

but the armoursmith increases hitpoints and gives certain defence options

barbs

gold upgrade means more hit points
elixer upgrade means strong armour that weakens mortar attacks, they only do half damage
dark elixer upgrade heavy armour that makes barbs immune to bombs and spring traps, like golem

its just an idea to band around, i think it would add more depth to the game and add a new strategy, also it makes the game last longer as you have more stuff to upgrade

you could add new upgrades time after time, like they do now, it extends the popularity of the game