I've been using spawn_entity.py in gazebo_ros for ROS2 to try to spawn a new camera. I really want this camera rigidly attached to a model that's already spawned in gazebo. I thought I could do this by spawning a new model with a joint from an existing base link but then I realized that doesn't make sense. Is there any way to spawn just a new link with a joint referenced from an existing model/entity?

I'm beginning to think that really the only way to do this is to remove the existing model and respawn it from a xacro that has the model updates I want. If that's true, then is there anything I should look out for to make sure there are no conflicts from the previous model? For example, this model will be receiving a twist message to keep it moving.