Among other duties, Vowles was in charge of Mercedes' young driver programme before joining Williams as a team principal this year.
Under his watch, Mercedes recruited several top-line prospects, including Italian prodigy Andrea Kimi Antonelli, who is rapidly rising through the single-seater ranks.
Now 16, Antonelli smashed through the karting pyramid in 2018 and 2019, which landed him a spot on the Mercedes junior programme in 2019 at the tender age of 12.
But with Mercedes and other teams prising away ever-younger prospects, Vowles now finds himself on the other side of the young driver arms race at Williams.
Currently, the Williams Driver Academy has FIA Formula 3 drivers Luke Browning, Franco Colapinto, Zak O'Sullivan and Oliver Gray on its books, as well as Indy NXT driver Jamie Chadwick.
But according to Vowles, a "void" below the mid-tier junior formulae might now force Williams to go further down the karting ranks to find the next big thing.
"The problem we have is that I think all the future champion drivers have been near enough signed up, up to Antonelli," Vowles said in an exclusive interview with Motorsport.com.
"You have to go younger than Antonelli now, so now we have a problem, the gap has been created.
"We have Zak [O'Sullivan] and we have Luke [Browning]; we have many other drivers but Zak and Luke in Formula 3 who have potential. But it's early days, in my opinion.
"What I'm looking for is someone who's younger than Antonelli, where can they end up. So maybe we have a void."
While admitting there is some frustration at tying the highly regarded Antonelli to Mercedes before his departure, Vowles says he is looking to bolster the Williams junior ranks in a similar fashion to his work at Mercedes.
"I was one of very few who created the Mercedes young driver was a programme, so I know how to make it," Vowles said.
"The frustration is I signed a very good driver before I left, Antonelli is in a good place.
"But I'd much rather create our own programme here, it's under my roof that I can control because the money is not a problem, we'll spend the money required to build it up."
However, Vowles would not be averse to taking Mercedes' junior drivers on loan if the right opportunity came along, much like the Brackley team loaned out George Russell for three seasons at the start of his F1 career.
He added: "It's not out of the question that if Mercedes wanted to put Antonelli here, I'd be interested in the idea like we do with George, if I don't have another driver of the same calibre."
Earlier this year Vowles revealed he had passed up on signing current Williams driver Logan Sargeant at Mercedes in the American's F3 days, which he since admitted was a mistake.
Sargeant was subsequently snapped up by the Williams academy and promoted to an F1 race seat.
"At the time in Mercedes, we had a good suite of drivers, so that was where my relationship with him ended," Vowles said at the start of the season.
"Williams funded him because they had a deep belief that he was the real deal. It just shows you that in my previous life, I was wrong and Williams was right."
