using states for a "charge magic" system

Until more plugins are made, I was hoping to use states to accomplish a magic system I'm thinking of using.

Basically, magic has to be charged for at least 1 turn before it can be used, and I want an enemy attack to interrupt the charge.

So I was thinking of doing this by having a skill called "charge magic" that the player would use first.  It would give a "add skill type: magic" state.  I would then make every magic spell remove this state, so after casting a spell you'd have to charge the magic again.  Finally, I would have enemy skills remove the "charge magic" state.   

Would this work? Or can anyone think of a simpler way of doing this? Thanks!

I would set the default so the only unsealed "Magic" skill is "Charge Magic."    All other battle-specific Magic spells would be Sealed by default for every magic using player.

When a spell is Sealed, it may be in the list but it's greyed out.

So, when a player does "Charge Magic," it adds a "Charged Magic" state to the player.  The state then unseals all of the various Magic spells.  This lets your players learn new spells but keeps the spells locked until the Charged State applies.

Enemy attacks would then always remove the "Charge Magic" state.

Thanks! Two questions: 

1) How do I seal skills by default? (So that they show up in skill list but are greyed out like you mentioned)  Would I have to add the seal skill trait for every skill, in every Actor?

2) How would I unseal them...would it just be using the "add skill type" trait?