NAF – New artifacts with unique properties.

Or could we create a system with a regular and an extended version, like NHF and NHF_E? The first would only include balance adjustments for multiplayer, while the second would include everything else. This way, almost any artifact could be accepted;
Also, the same principle could be applied to NCF.

People will still want to see a lot of things, even imbalanced ones, in single-player, but that would be problematic in multiplayer.