Would it be possible to have a feature that allows members to see how many members are currently LIVE on a topic/discussion/group?

Technically it is feasible for Tribe's team to build and implement this feature on your portal. However, as this feature is not on our roadmap and non of our customers has requested this as custom feature, you can requests this as a custom app, if you are an enterprise customer. Custom apps will be created and implemented on your portal based on the agreement you would have with our team about the timelines.