Republishing multiple cameras has unexpected results

This issue is probably a few separate issues and can be cleaned up, but I need to get the facts down and we can create smaller issues from this one.

Setup:
Foxy on ubuntu, latest apt packages
3 cameras:

• 1 and 2 using https://github.com/anqixu/ueye_cam
• 3 using https://github.com/clydemcqueen/gscam2

My desire is to run a single compressor if possible which remaps the /cameraX/image_raw to its compressed version automatically without complex topic remapping.

I have 3 problems which manifest in strange ways depending on my configuration.

Problem 1: image_republish doesn't detect that gscam cameras are the kinds of things it can compress automatically
If i run with ros2 run image_transport republish raw, Camera1 and Camera2 get the correct new topics (they don;t work but they get the correct remapping, see below). However, Camera3 does not. It is as if image_transport does not recognize that it can compress the gscamera feed? So, I run 2 compressors, one with no args and one with ros2 run image_transport republish raw --ros-args -r in:=/camera3/image_raw -r out/compressed:=/camera3/image_raw/compressed

Which leads to

Problem 2: either image_transport doesn't forward its "subscription" or the camera driver ueye_cam reads its subscribers wrong. Basically, if only the raw compressor is running, the driver never turns on the camera. I think this may be related to these issues:

• https://github.com/ros-perception/image_common/issues/111
• https://github.com/ros-perception/image_common/issues/114

So, with default node... i get the right topic but no data in them since the camera doesn't know it has a subscriber.

Basically, I cannot use the default. So I run 3 compressors

ros2 run image_transport republish raw  --ros-args -r in:=/camera1/image_raw -r out/compressed:=/camera1/image_raw/compressed
ros2 run image_transport republish raw  --ros-args -r in:=/camera2/image_raw -r out/compressed:=/camera2/image_raw/compressed
ros2 run image_transport republish raw  --ros-args -r in:=/camera3/image_raw -r out/compressed:=/camera3/image_raw/compressed

which causes

Problem 3: The /out topic exists after remapping and contains ALL camera feeds

Once I run the command above... i get /out with the feed of all cameras transmitting simultaneously. This affects ros bag -a because it will subscribe to an extremely large and non-nonsensical camera topic.

Start by reproducing the three cases with the listed image_transport republish commands under Foxy on Ubuntu, using the ueye_cam and gscam2 camera setups. Compare the discovered input and output topics with subscriber behavior, then split the findings into focused issues; done means each behavior has a confirmed scope and an independently testable expected result.