Pro sites and adsharing

On our Blog Network we have the ad sharing plugin and Pro Sites.
We have too levels Free and Paid the Paid Get more plugins and More Themes and Ad sharing the option to turn it off.
What I would like to do for the Amateur Radio Community is offer free Premium access to Licensed Amateur Radio operators but with no Turning off the Ad sharing on their blogs.
I'm at a loss how to go about it.
I was thinking about just creating a third level Amateur Radio Premium and they would get the same as the Paid Pro Site Premium level but don't know how to stop them from turning off the sharing of the ads on the ad sharing plugin. Is there another way I should go about it.
the end result is they get free access to paid Premium plugins and Premium themes but I would like to make money from their sites with the ad sharing.