I think you could also have this possibility - choose an app category and get the ad spots required.
And still - you could have more control and info regarding your app than just "you had x number of impressions in the last y days".
And still - you could have more control and info regarding your app than just "you had x number of impressions in the last y days".
Regardless, I think you're not really solving a problem. You're giving more information that involves more labor.
It seems like you're describing more of a labor/service company rather than a tech company, which is fine. But the more information and control you're giving the customer, the more labor/time you're expecting out of them.