It's either a genius design or deeply flawed. 10 second after Starfleet saw it perform, they must have been setting aside a few production lines in Oceania Planetia. Unless the flyer had to be vetted and reviewed like any new design for consideration, like how we saw that board strip Harry a new one about his new shuttle when he toured a different time stream... There was a war on. Does that mean these things were fast tracked or shelved? Did the/a Delta Flier fight in the Dominion War? If the testing on the flyer in the AQ went so badly, could they decommission the design completely and order kathryn to mothball her "original" Delta Flyer?
In the novels, they have. A shuttle "based on" the design of Voyager's Delta Flyer cropped up in Titan: "Over a Torrent Sea" and STO: "The Needs of the Many"
Ah, Oceania Planetia, the famous water shipyard. Given that the original Delta Flyer seems pretty capable underwater it seems like a plausible place to assemble them.
Sweet Jesus, I Orwelled myself! I wonder if when Orwell renamed England as Airstrip One that he had any idea that what the future would think he was calling the the once and future home of King Arthur was "Vagina One". Utopia Planetia. Thank you very much Sandoval.