[Snake]

As the title says... This is one less skill they can use natually without needing another class, which severely limits their options of blending classes around. And Soldier, being a base class, shouldn't really need to depend on other classes like Promotions often do.
Which then brings me to drink a mug of coffee and come up with a weird idea for it, don't know how well it would be accepted, but here goes nothing:

Enchant Shield works two ways:

The intended way. If you are enchanted with an Elemental Impact...

The elemental shield will grant resistance to the same element equal to X% (X = Rank*5) and will deal damage (ignores armor) to enemies who attack you or that you Bash equal to X. Guarding will double the elemental resistance and retaliation damage, but no effect is given when under Guard Break.

However, if you are not!

You will receive the effects of 'Elemental Interception' for 3 rounds, which will reduce your Move and Evade to 0 for the duration.
Upon taking damage, you will absorb a bit of Focus from the damage taken and enchant your shield with it, making the intercepted damage become the enchantment for the shield. Enchanting your shield this way, though, reduces the overall buff's duration by half (min. 1).

Alternatively, if above's too 'OP' for a base class, fret not!

Enchant Shield will utilize from your Talents. Your highest 'Potency' for the Elemental Talent tree will be used. (I.E, if your Potency points in Fulgurmancy is 5, your enchant will be Electricity.), but enchanting without an Elemental Impact will reduce the duration by half (min. 1).

There, now feel free to gun me down or offer constructive criticism, heathens.

[Autumn]

I don't have any comments on any of the current things mentioned here (Currently, at least), but I will say there is a way for non-mage class'd soldiers to use enchant shield now, via Elemental Forces, since they grant an enchant you can immediately use it for enchant shield should you desire.