Giolito, Lynn & Clevinger will all be gone after this season. There's no one in Birmingham or Charlotte who's any better than Kopech for 2024. It'll be dumpster diving again in free agency to fill out the rotation.
Even if Kopech is a ~5 ERA guy who can barely go 5 innings, that would make him the 2nd best starter in the organization for 2024. He has to stay in the rotation for the time being, even if he'll eventually transition back to being a reliever again