I concur that H&C is Lucius Malfoy. It seems very plain if you look at the proximate results instead assuming every character belongs in the cast of Death Note. A plan that requires that many conditionals is bound to fail.

-H&C succeeds in causing a 3 way tie: The school nearly riots.

-H&C gets Zabini to lie to Quirrell and Harry: Quirrell and Harry trust Dumbledore less.

-H&C messes with Hermoine so that she hates Draco: Draco and Hermoine stop being friends.

Not everyone has to be playing Xanatos Roulette. Some people can just use influence and get back solid and predictable returns from their actions. Lucious Malfoy makes good and predictable gains with each of these plans.