This was my first idea on how to utilize this. If a set contains a theme of putting counters on creatures, you could draft this to regularly have a way of doing that.

It does have the potential to give you overly flexible combats repeatedly; opponents will have to consider your ability to put a counter on any creature each combat. And if you have two of these, you can really pump up anything as long as you're willing to trade down in card advantage.

The Top Swap mechanic is meant to be gated by your willingness to go down on cards. Say you have seven cards in hand and cast this; you rummage, put this on top, and now you have six cards in hand. If you had two of these you could cast it six times over, but then you'd be out of cards. Seems fine to me!