I don't think the squad needs a complete overhaul. What it does need is the missing positions filled. Striker, center back, left back for starters. Get that sorted in January, and we can finish midtable.
Summer we need upgrades on players such as Gana, Schneiderlin etc who will become able squad players.
Plus we need a manager who has some nous. I'm surprised Koeman wasn't it given his stature in the game.