Your p2p nodes might not be behind NAT. In a lot of populations you can rely on everyone having working v6 for example.
I think the question of what's "pure" p2p is somewhat academic. If your app uses DNS, is it p2p, isn't DNS just a distributed p2p database? Does p2p require that every aspect of your app right down to discovery is distributed among nodes running your app? Is it cheating to use an existing DHT? etc.
I think the question of what's "pure" p2p is somewhat academic. If your app uses DNS, is it p2p, isn't DNS just a distributed p2p database? Does p2p require that every aspect of your app right down to discovery is distributed among nodes running your app? Is it cheating to use an existing DHT? etc.