No announcements were made about the future of his principal assistants, Nathan Grey, Stephen Larkham and Simon Raiwalui. Castle said their jobs would be discussed when Johnson took up his role.
"Michael's made some recommendations post his review and those recommendations will be discussed with Scott Johnson," Castle said.
She had spoken to Cheika about the decision to appoint Johnson and he was satisfied with the changed structure.
"We've had some good discussions with Michael and he sees that as a model that allows him to do what he's best at, which is coach the Wallabies," she said.
Johnson's focus mainly will be on off-field issues. He will lead a wider campaign to rebuild Australian rugby, which has fallen into a malaise, losing ground to rugby league, football and Australian Rules football.
He will oversee a fighting fund to help retain Australia's best young talent and will work to produce greater alignment between Australia's four Super Rugby teams. The teams have been fiercely independent, shunning a single national style or coaching approach.
Rugby Australia will now adopt a system which New Zealand has used for many years under which Super Rugby teams, while independent and competitive, work towards a coherent national style.
Johnson, 56, was Australia's attack coach under John Connolly at the 2007 World Cup.
"I am excited to be returning to Rugby Australia in the director of rugby role and I am looking forward to supporting Michael and the Wallabies in their build up to the World Cup," Johnson said. "I am also looking forward to working with the Super Rugby teams to build an aligned model that will enable sustained success for Super Rugby teams, the Wallabies, and ensure we maximise the opportunities for Australian Rugby."
In a statement, Cheika said the new structure would be "great" for Australian rugby.
"And I know it will prove to be the best long-term structure for the game in this country," he said.
- AP