I know this isn't the most important bug right now, but some of these would be super easy to fix, I'll check some more later, but for now I noticed that while Kingdom farms cost 25 gildar 2 materials, Empire farms cost 25 gildar 5 materials.
Also the Empire has no way to gain mana regeneration bonuses, so an Empire caster will always have lower mana than a Kingdom caster (once level 5 cities are present).
If you have some more that could be fixed easily please post.