I want plenty of air pockets, not just for practical reasons in his own film, but also for the others like Justice League or any other crossover he or his kith and kin may have like Teen Titans or Young Justice, and because I think there can be some fun use of air pockets in his film mythology.
For instance, let's say that Atlantis's capital has a significant number of surface dweller subjects who act as a lower caste system, sorcerous Guinea pigs, and new donations to the gene pool, all for he, trapped and corralled in domed cities and subterranean tunnels. These would be people captured from raids against surface dweller navies, salvaged from sinking ships, and maybe even the descendants of original Atlantean peasants, slaves, and servants, as well as survivors from any other sunken cities that the Atlantean Empire may have captured over the centuries (like Ys in Brittany). You now have a population that can produce someone like Black Manta as someone who knows Atlantean culture, language, and technology, while still being an outsider who has a grudge with certain Atlnateans. Personally, I'd see Black Manta and his men starting as a Janissary-style bodyguard to the nobility, before they gradually shift to being a renegade faction with a personal feud with King Arthur Curry.
The way I see it, air pockets and domed cities enable for a fascinating development of Atlantis in terms of politics and culture:
1: High ranking Atlantean nobility gains full mobility in both surface conditions and underwater conditions, and get a place to flaunt and exploit their superior strength and toughness among mere mortals, and to train for any conflict on the surface. You also have a place for them to get the fully developed and ugly spectrum of prejudice: some would see surface subjects who can't leave their homes as parasites, others will act faux-paternal towards these "pitiable wretches", and some would simply objectify them as literal human resources.
2: You get four potential different castes for Atlanteans. The upper caste can move in both sea and air, looks human, and preserves what's left of their original culture. Then you'd have the humanoid mutates, like King Shark and Lagoon Boy, who are equally adaptable and intelligent, but are outsiders because of their looks. Then you'd have the utterly transformed mutates, like the Trench for the bad and the mermaids and such for the good, who are so divorced from whatever humanity their ancestors had that they don't even really understand the Atlanteans. And finally, the mortal humans who are trapped scraping by in tiny world's enclosed in darkness controlled by their masters.
3: We get a scenario where mixed-Atlanteans and surface dwellers have enough precedent and predecessors that there can be a real blending of the world. Black Manta's son can be both concealed among Atlantean nobility and still very clearly a product of diverse integration of surface dwellers to Atlantis's people. Arthur can have a vested interest in seeing peace installed in Atlantis that can preserve all lives. And Orm can get that weird world view where destroying the majority of the surface world is okay because they'll just subject the survivors under the sea.