Why Not Create a Network from Dropped Domains?
 

If dropped domains have a good backlink profile and can get re-indexed, why not only buy them instead of ones that are still indexed? What am I missing here?

Once your domain get dropped means all the issues related to it also get drops if it is right or wrong. so it is better to leave it.

If your domain drop so all the techniques related with domain have must be drop down. So you should purchase a new domain and work for it.