I do think the Lounge has some uses, for example on another forum I was on they used it as a way of notifying us of upcoming changes to the product before the news was released, so that we could give feedback and out views on it.
On the flip side, some use the Lounge or something similar to talk about others behind their backs, so that’s something I don’t like the Lounge sometimes. But in more peaceful/civil communities, it remains fairly quiet unless there’s something important.
I have been on some communities where honestly, the Lounge had nothing going on that getting TL3 access wouldn’t matter - you didn’t miss out much.
You might be able to add the user to a separate group once they become TL3, and have the Lounge tied to that group instead of the TL3 group. This way, when the user loses their TL3 status, they still have access to the restricted category.