My main knowledge is of the Inverness lounge, although mainly in Scotrail days, I'm very rarely on nowadays, but I understand that custom and practice is still pretty similar now, and it's got very little to do with what Serco say or do before anyone gets too far into that. It's what the crew does that makes the difference.
Off the point, I know a very funny story about treatment dished out to an overspill Inverness passenger in a far from busy Aberdeen lounge way before the days of Serco, and I may well come back to that...
As I recall there are two ways to run the Inverness lounge, mobbed as it is on departure.
One way is to leave the Team Leader and, apparently nowadays, a second person in the kitchen, toiling away from 830pm until at least 1030pm. They don't have time to allocate seats or suggest pairings of individual passengers, or think about when to ask people to come back when a table might be available. They may well fall back on 'rules' as a backstop. The queues and frustration build up and people are standing both in the aisle and down into the first sleeper carriage. Significantly, hosts are nowhere to be seen.
Or the full crew work as a proper team and flood the lounge with staff as soon as they can get down the train. I'm thinking of an Inverness crew under the legendary David, who I think emigrated to South Africa a couple of years before Serco took over.
The Team Leader's first job is to seat and take orders from passengers as quickly and efficiently as possible while the second person (under the new system) runs the kitchen. Seating will certainly involve putting strangers together if needs be.
As soon as they know that their sleepers are occupied and settled the majority of hosts join the lounge effort and tables can be served, cleared, bills produced and customers sent happily on their way with amazing speed - you can have five of them on the case after all. Cheapskates lingering with no more than a cup of tea get the message pretty quickly with this level of activity around them. The Team Leader continues to consider those waiting, whether in the lounge or in cabins, and finds them tables just like the maitre d of a decent restaurant might.
Maybe they do need more systems and rules, but my recollection, and occasional current experience, is that the space they have used proactively and efficiently by a good team, who can be bothered, can be made to work extremely well to the extent that it looks like an advert for VisitScotland.
If anything this should be easier in the mk5s because the stupid purple sofas have been replaced with seats or stools at proper tables.