I follow the logic, but I think Amla is too much of a niche player to go with it. With him opening, he provides quick scoring and stability at the start and stability in the middle. Drop him down the order and you just get stability. Career wise I think he probably scores quicker in than qdk in the power play- similar strikerates, but qdk accelerates and Amla doesn't. He's fading a bit, but I'd rather see him open until he retires.
Markham seems like a naturally quickscoring bat. I feel like he'd play the same type of innings whether we were 0 or 1 down.
Quotas- Andile, Hash, Rabada, Duminy, spinner, Ngidi. Hit the quota numbers if we play all of these, but only Hash, Rabada and spinner are sure spots for now. If the black bowlers don't come right it's going to end up limiting opportunities for new white bats. This said, with WC coming up, there's probably going to be a lot of chopping and changing, so everyone who deserves a look should get one.