> For example, the players may want to wants to mod the game-server with features, bug-fixes, or moderation-tools, while the publisher wants a strict lockdown to their artificial monopoly on "digital goods."

Then the mod must be loaded & run on the server's end, with its logic enforced on all players on that server. The client shouldn't have free reign over the server's internal logic & state.

The one exception to this are visual mods that modify the presentation. But even then I'm skeptical, as modifying the presentation layer can affect the decisions that X makes, or even worse, give them an unfair advantage that other players should also have if X has them.