Canada's Wonderland has Behemoth which is a Hyper and Leviathan which is a giga coaster. Both do provide different experiences as Behemoth is about the airtime and Leviathan is about the speed. As I have visited Kings Island a couple of times during the past four years, I feel a giga would be a perfect fit for the park and compliment their already awesome roller coaster collection. I really need to get back sometime soon to ride Mystic Timbers as it was under construction the last time I was there!
I definitely agree that having a hyper and giga in the same is perfectly fine as long as they focus on different things as you mentioned. Also... you definitely need to come down to ride MT! It's a spiffy little ride!