I’d probably go for a Foxface over the Powder Blue Tang although IMO Foxface really do best long term in at least a 5’ tank.
Powder Blues along with many other species in that group of Tangs are too active and nervous for the average sized aquarium. Powder Blues are also notorious disease magnets.
A Blue Throat Trigger I’m not sure would do well in a 4’ 100, I’m not sure about their expected size in captivity or their swimming patterns so I’d ask. However one tip I can give you is that this genus of triggers that includes the Blue Throat are pelagic rather than reef associated like some others. If that’s any indication as to their activity levels, I’d want to allocate a fair amount of swimming space and I’m not sure if 4’ is enough.
As for butterflies keep in mind the vast majority of species are difficult, with a good number of them being obligate or significant corallivores. I wouldn’t even think of trying most species of butterflies unless I was top notch in my ability to get them eating prepared foods or have a very mature SPS dominant or SPS only tank that’s also very large. People have done it but it’s not for the faint of heart (or wallet). There is a guy (don’t think he’s posted for a while) called SDguy who has a 240 FOWLR with some of the more advanced species of butterflyfish, I’d contact him via PM.
Remember that no butterfly or angel can be absolutely guaranteed to be reef safe. Not even Tangs and the Rabbitfish you’re considering for that matter. It’s not always them eating the corals themselves, in the case of some Tangs and Rabbitfish, but the coral cells and micro organisms are what they’re really after.
To my knowledge, the deepwater Roaps subgenus of butterflies (Tinker’s, Declivis, Marquesan, Mitratus, Flavocoronatus) have been successfully kept in reef tanks. The Copperband and Yellow Longnose (Forcipiger Flavissimus) have also been kept successfully by more than a few people in reef tanks. The genus Prognathodes are deepwater or subtropical for the most part and might thrive better under cooler temperatures. Roa is less frequently seen as other than Modesta, the majority are found in very deep water where corals might not be as abundant, so might be worth a try (if you ever find one, that is). Chaetodon Guentheri, Chaetodon Sedentarius, Chaetodon Millaris (Biota’s bred them before but haven’t seen any in a long time) might also be worth a try. The genus Hemitaurichthys (Yellow and Black Pyramid) are the planktivores among butterflies, there’s still a chance they’ll munch on corals but they have a relatively good reputation among butterflies when it comes to corals.
As for angels, I’d be inclined to not have one but a pair of them in a 4’ tank. Depending on the size you get your Coral Beauty, generally the route to forming a pair or harem is 1 big and the rest smaller or you start with young juveniles and give them ample hiding spaces. Centropyge need swimming room but are closely associated with the reef, which means rockwork that lets them swim in and out is their natural preference.
The rest of your list looks fine. I’d have slight worries regarding the Flame Hawk and the Shrimp and Goby pair, people have done it successfully so it may work out well for you but I’d establish the Shrimp and Goby pair before the Hawkfish if possible.
There’s a fish, maybe even a pair that I’d consider over the Foxface or a butterfly: Biota’s Marine Bettas.
Another factor I would consider is, what kind of look do you want your tank to have? Many people like their tanks active and fast paced with fish going back and forth. Some people (me included) prefer a tank where the fish are much more leisurely in their swimming style and where the moving “picture” doesn’t appear to be in a “rush.” Many people (perhaps a majority) prefer to have as many species of fish in their tank as possible so they can have lots of variety, but there’s also some (of which I have converted to over the course of some time) that prefer the social behaviors of fish rather than stocking as many individual specimens as possible. This means creating as many pairs or harems (if the tank is big enough) as possible. If you want to go this route, it would be helpful to study the biology (especially with regards to their sexual allocation, some fish change sex and some don’t) and reproductive strategies of the fish you’re looking to form pairs / groups of.
There’s also some people that are super hardcore about one or maybe two families of fish. Wrasse dominated tanks, angel dominated tanks, butterfly dominated tanks etc. Personally I’m a big fan of angels but I also want some non-angel types of fish so I’m somewhere in between a “generalist” and an “exclusivist” in the sense that I’d always want my tank to be centered around the angelfish, but not at the cost of forgoing other types of fish entirely. From the looks of it you’re clearly a “generalist.”
On a final note, I am a strong believer in buying captive bred whenever possible so I’d take a look at Biota’s website or maybe LFS in your area that gets ORA stock and / or Biota stock.
Good luck with whatever you decide.
