It's okay. This year when Cedar Point opened that new country stage in the back of the park by Maverick, that made that path really tight too. I'm sure Cedar Fair will make sure Kings Island has plenty of space over there.
However, with FOF and BLSC both being Premier-built, there could be some convenience found in having a third coaster from the same manufacturer (when acquiring replacement parts and service).
Ultimately though, I would think (and hope) that they go with Mack, for the reason you stated...
The flyers are coming back.
Have you ever wanted soar like a bird over majestic mountains? The Mountain Gliders, opening in Carowinds’ all-new Blue Ridge Junction area in 2019, offers an experience that’s mighty close. After boarding one of the unique carriages, you’ll start spinning at a high speed, so much so that you’ll spin outward and rise to 28 feet above the ground. Once in the air, you take matters into your own hands by operating the carriage’s controls to command the glider’s flight. Whether you explore the high altitudes as if flying above the Blue Ridge Mountains or cruise at a lower elevation in the valleys, the choice – and experience, mild or wild – is up to you.