Hm, does this mean our enchantments have to be elemental-flavored? I was thinking something more force-ish, like arrows that seek their target or a saddle that feels completely steady to the rider. Maybe we could justify the first one as air magic?
I'm thinking an early game strategy of excellent horse archers could segue into flying around on magic boats or carpets and shooting cannons (fire elements right?) or guided ballistae in the late game. As an added bonus, the horse archer strategy should give us an advantage in the beach area, which is supposedly where the good wood is (further bolstering our archers). Maybe something like...
Mighty Bow: A firm, good quality recurve bow with an air gem set in it. When an arrow is loosed, the air magic accelerates the arrow to a speed much greater than it would normally reach. Ideally, the amount of power used should balance out so that the recharge is only a few seconds, allowing a steady rate of fire.
Seeking Bow: A firm, good quality recurve bow with an air gem set in it. When an arrow is loose, the air magic of the gem steers it towards its intended target, so that an arrow which might have missed by some margin will find its mark. Depending on how much power is needed to make this work, it's okay if the gem recharge slows the rate of fire somewhat.
I don't know if the seeking bow would rely on some clairvoyance magic we don't have, or what, but the mighty bow should be a reliable pick.