Well if no one opted out of any data type then it would be just like the some systems we have today. If most relays opted out of a data type x then the result would probably be that data type x would be less anonymous then other data types. It would take fewer conspirators to subvert the system for data type x. Similar to anonymity from government Z is effectively lost if they control m% of the nodes on tor.
Though I do not study cryptograph professionally that would be my current guess.