I think adding a !ping command for lobby leaders would be extremely useful, to give a sound notification to that person targeted. (eg. "!ping 96drum" would give a small ping notification to me) Preferably, a !ping all command would be good as well. A 10 second or so cooldown would also be a good idea, to prevent abuse by trolling lobby leaders.
This would be good for lots of situations where you want to contact someone and they've tabbed out. For example if your friend suddenly wants to join your team, and you want someone to switch to the opposite team. Or if you want to ask your team to join mumble, you can "!ping all" to get their attention.
I'm don't know much about developing, but I think that's already a feature that admins can do in the main lobby finding page (for regions, if not specific people), so I assume it wouldn't be too much work to port that over to the lobby page?
Alternatively, it could be buttons by each persons name, next to the kick and ban buttons.
Thanks!