The blocking feature would need a rework for Open PP, as it would be ridiculous in a feature about conflict that you can block someone for shooting you.Which would be against the rules and anyone doing so should face punishment. Same goes for anyone modifying their router or firewall to stop themselves instancing with others.
On the other hand, someone could build up an impressive block list and after a few encounters and runs through enemy systems probably have a majority of opposing players blocked, and that would be totally legit.
Lateralus has raised the issue of bots, and bots could be scripted to also add to their block lists, so his hopes of shutting down bots, or even spotting them, might be problematic. You can't see them, you don't know they are there, which brings us back to the same situation we have with modes.