1. Ip address is used for peer identification.
In general IP address for peer ID is a bad idea. For example, running over tor, proxies, running with IPv6 (eventually) when IPs will be quite plentiful and could essentially be switched every hour or whatever etc. IDs in a p2p system without a central authority are problematic. ;-)
Exactly! IPs would be a nightmare. Which is why my current thought is to use a pseudonymous bitcoin address for identification (distinct from the addresses used for payouts), and to make it economically advantageous for a node to pick one and not change it over time