It’s plausible to do what you’re saying. I still think it’s more trouble than it’s worth. If you somehow managed to engineer everything perfectly and tune it as you say, you’d still have customers who wanted their service to stay online past overcharge. I’d think the predominant business case for such tight guarantees would be small and low budget projects. Additionally, every cloud vendor who doesn’t do this seems to be cheaper, so you’d be priced out (in a commodity market).