If he added a significant amount of fish say in the last month I would wait a few weeks to add anything further. He does have a maintenance company for it but they to be honest, are most likely more concerned with selling stuff than the actual tank and it;s best interests.
if it were my tank the next thing i would add would probably be two yellow tangs or a yellow tang and another tang of some sort, and at the same time as they can be kinda aggressive if added at different times. The blue tang is known to be a big mush so I woudln't expect aggression out of him.
The other fish i would consider would be an anthias or an anthias harem of a couple, with one male and maybe 3 females. they are spectacular fish. Bar gobys are nice too. So may options with such a large tank.
here is a link with like every fish imagineable and their tank requirements and tempermeant as well as diet.
Aquarium Fish: Tropical Freshwater Fish and Saltwater Fish for Home Aquariums
i would stay away from angels as they arent always reef safe just fyi.
Most of the fish he has are small so there is room for more. Alot also depends on his filtering capability and current bacteria colony. You add too many fish at once and the bioload can cause huge spikes in parameters leading to possible death.
As long as the tank is being monitored for water parameters then corals he can add at will. Anything from australia is usually awesome and sought after, but also expensive. i don't think the money is an issue with your boss though. lol
The site above also has corals to pick from too, and their requirements.
I would also recommend some more cleaner shrimp and maybe some fire shrimp. I had 5 cleaners in my 6 foot 125g and they were fine until a shrimp killer took them out. lol
The only shrimp you have to worry about are coral banded ones, they are really great shrimp but you can only have one or a mated pair, they will kill each other off. But the cleaners and fire shrimp would be some great new additions.
do you know what his equipment list is? Such as a sump, refugium or wet/.dry filter? Or how much live rock he has? The live rock is the majority of the filtering in a sw
tank. Also what kind of skimmer is he running? Thats very important too with alot of corals. And last but not least, his lighting setup. that can make or break his setup on corals and anemones. (which i really dont recommend at this early in the game)