If an opponent taps a land for mana, that land won't untap on its controller's next untap step
Luckily, most of those can easily be replaced by any half-decent lands you want, especially in a 5-color deck
Planeswalkers are generally worth attacking, and then we come to the remaining categories: graveyards, hands, libraries, and lands
Interrogate Them Exile the top three cards of target opponent's library
On the other hand, if the Surveil mechanic does end up having an entire archetype dedicated to it, this will absolutely be a four-of in every single iteration of the deck
What makes Belle shine is her brilliant effect: whenever an opponents character challenges her, they have to discard their entire hand