Suggestion | Custom Argument Types

Currently, registering custom argument types (implementing ArgumentType<?>) will prevent clients without that registered argument type from joining. If not registered in the Registry.COMMAND_ARGUMENT_TYPE registry, apparently it should allow vanilla clients to join, but all the helpful stuff like command suggestions, etc. will not work for that type.

I'm suggesting a PolymerArgumentType<?> that implements ArgumentType<?> and presents itself as a standard StringArgumentType to clients.