I thought about this idea, and another one came to mind: to add functionality so that the Eagle Eye skill allows you to immediately copy all of the opponent's spells into your spellbook upon contact. That is, the opponent attacks you – he has an explosion in his spellbook. Your first turn – and you already have all the spells that he had in your spellbook. At the basic level – up to level 3, at the advanced level – up to level 4, and so on. The Artificer should also be left as is. IMHO, that's when the skill will be useful and beneficial for mage heroes.
Or, you could add another functionality: so that the one with Eagle Eye can see what's in the opponent's spellbook. This would be a good advantage in battle. For example, on the expert level, it could show the elemental upgrades as well.
The idea is generally amazing, but it still seems like a too overpowered skill, to be honest. Although, on the one hand, if you don't have a 5th-level Grand Magus, even if you steal an explosion, you still can't use it. But on the other hand, the opponent runs around, collects elementals, gets spellbooks, and then you attack him, and all the magic is yours.
The idea is good, but you need to think about how to make it right so that the skill becomes useful and at the same time not so overpowered