The Elemental structure of Magic used in YS is just one way to model it. It's not really about elements, it's about what those elements represent.
Just like you could use the Asian Elements to structure your magic, you could come up with a totally new one.
You could base magic on different emotions just as easily. Maybe something like: Anger/Love/Hate/Fear/Serenity. Now you describe those fields of magic and assign different effects, and voila, a new form of magic.
So, I'd say you should feel free to build your own system, no need to cling to the "classical" 4+1 element structure.
As to how powerful it would be. It would need to be a full form of evocation/thaumaturgy, so basically it's just as powerful as any other mortal magic. It's just another way of describing it.
What it, in the case you have given here, would not do is act as Seelie/Unseelie magic in any way. It would not, for example, satisfy the catch for someone vulnerable to either of those forms of magic.