What is the proper approach to create a dynamic *number* of subscribers/services?

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I have n number of robots, and I want to gather each of their positions. Each robot is under a different namespace so I have the topics:

/robot1/pose
/robot2/pose
/robotn/pose

If the namespace follows the same convention, is it better to:

1. Create a subscriber for each robot?
2. Create a service-client for each robot?

And given a subscriber or service, what is the proper way to dynamically find the services/topics to subscribe to?

Thoughts:

1. Use the parameter server with the number of robots. Works for both subscribers and services. Use the same callback for each robot.
2. Have each robot republish their pose onto a joint /pose_all topic and use one subscriber. Can differentiate between robots using PoseStamped. Simplest seeming solution (no parameters to remember to update...), but is it hacky?
3. Some better method using service calls?