Gowers, who played for the Western Bulldogs from 2018-2020, was recently named vice-captain of the club for the 2023 season.
Hannebery retired from the AFL last year, dealt with an injury interrupted last few seasons at St Kilda, after 224 games at AFL level. The three-time All-Australian committed to the club last week, and is under no pressure to line up in Round 1.
Senior coach James Byrne welcomed Hannebery to the club, calling the former Saint and Swan a "phenomenal trainer".
“Dan's just jumped on board so we are looking forward to him coming in and setting a standard,” Byrne said to the Herald Sun.
“We know he is a phenomenal trainer and just an out and out professional.
“To get a person with his CV to the footy club is just phenomenal.”
Naismith meanwhile joins the club after departing the Swans in 2022 after managing just 30 games at senior level across an injury interrupted career.
The 30-year-old has also signed for VFL side Port Melbourne this season, set to play for the Xavs outside of his VFL commitments.