That's an interesting idea. I think the effects should both happen to the same tower, possibly a random tower rather than highest or lowest level.
My problem was that the level reduction seemed pretty minimal compared to a boost in base damage. The effect I placed would either force the player to find a good position where FoY only targets 1 tower, or create a balanced defense, which isn't supported by the current meta. But with the season event and new cards, it might just work.
Ygg + Potion Splash + FoY can create a pretty crazy tower setup, and can even balance out Metro and Darkness teams to have multiple carries(low level Mr. Iron gaining base damage boosts, Shadow spam, etc.). Of course, this would make Wolf comps pretty OP late game I would think.