Creating unrelated tables in ROS2 bag file

edit

We want to record additional data during both recording and playback of a ROS2 bag file that doesn't fit into a topic message. Since the default ROS2 bag file format is just an SQLite file (let's assume we can guarantee that it won't change), is there any reason why we cannot or should not create and write to our own tables within a bag file? Are there any issues we should be aware of before trying this?