Technically you've just summed up Roger, Grover & McPhee. Why do we persist with players the same ilk that provide less of a role than a reigning AA could?
Well, Roger is gone and a lot of people would agree regarding Grover and McPhee. However with Grover definitely and to a lesser extent McPhee, they are known quantities regarding their performance, strengths and weaknesses, fitness, training needs and management. They know the game plan, know their peers, have chemistry with the rest of the team, are established leaders and are integral to the side. McPhee was also brought in for his physicality after Sollie retired when most of our lads were skinny whippets.
Bringing in someone from from outside is a much bigger risk. None of that stuff is really known about Leon and I would also disagree about them being the same ilk as Leon.