The phrase "a vast scheme" is correct and usable in written English.
It can be used to describe a large or extensive plan or arrangement, often with complex elements involved.
Example: "The government unveiled a vast scheme aimed at improving public transportation across the entire city."
Alternatives: "a grand plan" or "an extensive project".
The book is constructed like a vast scheme of lectures, with points clearly enumerated.
The indictment, a rare criminal action against a large corporation that followed years of the government charging SAC employees with insider trading, highlighted a vast scheme that played out over a decade.
On the tape, the official, Jean-Claude Méry, who had since died, described a vast scheme that collected money from just about everyone who wanted to do business with the city.
On the cassette, the aide, Jean-Claude Mery, who has since died, described in detail how a vast scheme for gathering kickbacks from people doing business with the city worked.
In addition, to any charges stemming from the Mery tapes, judges are also looking into a vast scheme involving kickbacks on school construction contracts in the greater Paris region.
Government officials say the Somalis here were unwitting participants in a vast scheme to use legitimate financial transactions to generate cash for Al Qaeda, the terrorist network of Mr. bin Laden.
We have a role in this vast scheme of things.
Even as lawmakers in London hammered a top Barclays executive over the bank's role in a rate-rigging scandal, another financial firm that is largely owned by the British government is fighting an investigation into the vast scheme.
For much of Wall Street, the expertise that once was expected to elevate China's financial system increasingly looks like sorcery, or a vast Ponzi scheme in which banks borrowed vast sums, lent to virtually anyone, and used incomprehensible models to convince markets that all was fine.
Last week the PD mayor of Venice, Giorgio Orsoni, was one of more than 30 people for whom arrest warrants were issued on suspicion of involvement in a vast bribery scheme surrounding the lagoon city's €5bn (£4bn) dam system.
Mr. Madoff is accused of operating a vast Ponzi scheme.
