I would find it annoying for the platform team to readjust the specs of the pods I'm running on. To give insights is valuable, but otherwise it's an invitation for incidents to happen.
It happens shockingly often that applications only support working with a single replica and even worse when those applications cannot run concurrently with replicas of themselves which prevent smooth rolling updates.
IME if applications are fault tolerant of restarts, or support concurrent replicas then scaling up and down to meet demand is absolutely fine.
Also this reads like a cry for help:
> Therefore, to keep our Kubernetes clusters optimized, it would necessitate mandating all teams to perpetually engage in complex manual optimization processes indefinitely, or until Mercari goes out of business.