I'll say that I really like your ideas and planning, but that this subject can be a bit more complex than perhaps what you've realized or than what one could glean from my article.
For instance, what exactly one means by "murky water" or "lagoon" can vary widely and is important in determining which species can grow in a place.
For instance, some areas with turbid (=murky) water have only a few meters of visibility due to a lot of suspended colloidal material in the water from a river. Think of a muddy river emptying into a bay. Some corals thrive here while others don't tolerate the conditions at all. This is true even within the genus Acropora. Most Acropora won't deal with the sediment, but here and there some species will do just fine. I've seen various bottlebrush species and a few corymbose (e.g. A. millepora) in such conditions and they appeared to be just fine. Montipora, Galaxea, Hydnophora, various mussids, Porites, etc. would be more likely to dominate these areas than Acropora. Mostly what is controlling this dominance is a coral's ability to shed sediment via mucus, etc. Corals that are good at getting rid of sediment easily outcompete those that aren't good at shedding sediment. Most Acropora aren't good at this (though a few seem to be) which is why they tend not to be dominant here.
On the other hand, some lagoons have crystal-clear water similar to what is on the outer reef and many Acropora spp. are very, very common. In fact, usually one sees big stands of staghorn Acropora (they DO NOT grow on reef crests, not sure why people insist they do) in lagoons with clear water. There is a huge variety of corals that will grow in a lagoon like that though. The water is clear and the light is bright in the shallows, but there is protection from storms, etc.
Also critically important is the degree of water motion in a lagoon. This can vary markedly and is a very important control on species abundance. In a lagoon where the water flow is very sedate the dominant group of corals will probably be Porites spp. If the water flow is strong (for a lagoon) we'll see domination by branching Acropora. In between those two and faviids/mussids become the dominant groups. This has to do with physical features of the lagoon, tidal currents, etc.
As for nutrient levels in a lagoon vs. an outer reef, this is mostly determined by where the inputs are coming from. If a river is flowing into a lagoon it is going to impart a lot of organic material. The water may still be relatively clear (though not as clear as further from land) but there will be more particulate material. It is important to note that while this lagoon is usually considered to be more nutrient-rich than the reef slope away from land, this is mostly due to a greater amount of particulate material/plankton in the water column, not so much due to elevated DIN and DIP, though those can be slightly higher as well. In general the DIP concentration in a lagoon is about the same as in a very 'nutrient-poor' reef slope. The DIN concentration tends to be very slightly higher, in general, but still much below a "0" reading on a hobbyist test kit. Also, getting the amount of particulate material into tank water as compared to what's normal in nature usually proves tricky.
So I guess my suggestion would be to think of the species composition and what will thrive in the tank being controlled less by nutrient availability, as this usually is not very important in nature--there is usually enough particulate material anywhere for the majority (though not the entirety) of coral species to survive). What will really be controlling what can live in the tank, which parallels the controls in nature, are light intensity and water flow strength.
For a lagoonal tank it wouldn't make much sense to include a digitate Acropora as it would be very rare to see optimal water flow for this coral in a lagoon. When they (rarely) grow there they usually assume a very thin growth form and my guess would be that they do not do nearly as well as elsewhere on the reef (reef flat, upper reef slope). On the other hand, it would make a lot of sense to include staghorn Acropora, or some of the digitate and plating Montipora, or Porites, or Hydnorphora, etc. because those would all naturally be found in a lagoon (more water flow for the Acropora, less for the Porites, most others in the middle).
So, to get back to your questions a bit more directly, yes I think this tank is very plausible (I've had the pleasure to see tanks like this several times actually and they work quite well) and a good idea. I'd keep corals like those mentioned above--plating and digitate Montipora, Hydnophora, Fungia, Porites, Favia, Goniastrea, Lobophyllia, Symphyllia, Galaxea, maybe Trachyphyllia (depending on light intensity), etc. Acropora should do well in higher flow spots, especially if they have thinner branches. Bottlebrush species should be fine as should many corymbose and bushy species. Staghorn species, especially with thinner branches, should be fine too. There are other corals still. There are a ton of zoanthids, mushroom polyps, soft corals, anemones, etc. that could go in tank like this too. I would not recommend mixing all of the corals I've mentioned above, but this should give you an idea of what is naturalistic and likely to work well for you.
If you have any other questions feel free to ask.
Best,
Chris