The person servicing the aviary should always service the quarantine birds last, and shower and change shoes or use a foot bath in and out of the building. The species you have mentioned are susceptible to polyomavirus, especially the macaws. Since you brought up the economic issue, I would vaccinate the flock against polyomavirus because this will ultimately be cheaper than testing, especially if you come up with some positive birds. The diet should be changed gradually from seeds to a high-quality, pelleted ration taking particular care to notice that each individual is eating and active. If any bird is thought to not be eating, then the task of weighing these individuals daily may well prevent a death from the lack of food intake that can occur when birds are stubborn about converting from seed to pellets.
Skylights are a wonderful, energy-saving tool.
I have seen natural light produce extraordinary results, especially in birds that have not had adequate lighting in the past. Another topic you brought up in your question was the concept of a closed aviary. First, I do not believe that such a thing exists for most people. Pacheco's disease is a herpesvirus infection of the liver. I have known two aviculturists in the past who have been severely hurt both emotionally and economically by the closed aviary myth and the devastation of a Pacheco's outbreak.