Additional Features to Pro Sites

I would like to add some features to my Pro Sites site, but am not sure how.

I would like to give my member the ability to download PLR blog content as well as order additional content from me through their Dashboard.

How could I go about doing this?

Ideally, I'd like to offer a number of plr blogs depending on the level they sign up for. Then also give users the opportunity to purchase access to individual plugins instead of grouping them all together in packages.

Thanks.