Sure you can: People examining each other's work deter corruption and also have a good chance of noticing it. Only if a reviewer and a meta-reviewer collude to mis-review do you have a problem, and that should be rather rare.

Sure, in theory. Another theoretical but entirely possible situation is you get a black market of colluding citations. Consider this analogy: a company has workers and it wants to ensure they are working efficiently instead of chasing promotions. So they add managers. And managers for the managers. And manager for managers for managers. But in the end, everything is drowning in inefficiencies because everyone is still chasing promotions. Without addressing the root problem, it won't help to add more of the type of individuals who are prone to succumb to perverse incentives.