The phrase "a vast one" is correct and usable in written English.
It can be used to describe something that is large in size, extent, or scope, often in a comparative context.
Example: "The ocean is a vast one, stretching beyond the horizon and teeming with life."
Alternatives: "a large one" or "an extensive one".
"This was a ceremonial centre, and a vast one at that.
It follows that we are best off when we understand things least, because "a tiny confused idea is always greater than a vast one which is clear".
The water pollution problem is a vast one with which Federal and State leg islators, the boating industry and others have been strug gling.
The Exhibition Road project is a vast one, creating a new underground 1,200 sq metre space for big, temporary shows.
Whether gathering testimony from filmgoers, or unearthing old scores in archives, the project to discover what cinemas in the silent era really sounded like is a vast one.
Children walking along Del Obispo Street from Capistrano Valley Christian School took time to notice the rich colors in Reggie and Luisa Nieblas' garden in San Juan Capistrano--a vast one by current suburban standards.
The talk said Wahidur and some 30 other children had died after taking part in a vast one-day public health campaign supported by Unicef, with aspersions cast on multinational drug companies.
Mr. Foxell has surrounded himself with a vast, one-of-a-kind collection of sculptures and artifacts, many poignant, some unsettling and a few ghoulish.
I sipped microbrew tasters at Le Saint Pub, then moved on to sipping coffee in a café beneath the three steeples of Maison Mère, a vast one-time convent converted in 2017 into a creative, innovative space that includes accommodations, a museum and studios surrounded by the nuns' impressive gardens.
More editions came out, and he left annotated copies for a vast posthumous one.
