Something that would quickly come to mind is something like dim-sum or high-tea adapted to evenings and crowds of varying size. Probably just changing the foca

Something that would quickly come to mind is something like dim-sum or high-tea adapted to evenings and crowds of varying size. Probably just changing the focal point from the bar to the buffet and encouraging seating instead of standing would create a completely different atmosphere. Another variable you could consider playing with is moving from self-service to being served; where the waiters are instructed to dial down the frequency when guests get too far along. Ironically enough unlimited drinks is something that could work fairly well in this context, as long as the implication that excessive boozing is discouraged and will not be enabled by the waiting staff.