I'd like to very much encourage protobuf as the serializer, but supporting others both gives users the freedom to pick their own tradeoffs, and makes it 10x eas

I'd like to very much encourage protobuf as the serializer, but supporting others both gives users the freedom to pick their own tradeoffs, and makes it 10x easier to transition from ROS or another framework. We do support JSON output from the serializer layer - I'd rather not do other conversions if possible.