I fully support this. We had the ability to turn someone completely invisible back in a virtual world coded in 1995 (I know, I was a GM there with the ability to zap it.)

You CAN end up in an party with someone on your black list, however. I rolled into a World of Darkness with a dude who was on my blacklist because we both came in from Duty Finder. I was DPS, he was healing. That was kind of awkward. I couldn't see anything he said in party chat and he couldn't see anything I said in party chat (I think.) The exception would have to be made for when you're in a duty with someone on your black list, then they are still visible.

But open world? Yeah. Ghost their butts on my client. I don't even want to see them.