I think it becomes a really 'specialist' position when there's only one in there, whereas when you're playing a 4-2-3-1, you need some variety, ideally with one positionally-wise and metronomically-passing, as in Makelele or Bridcutt, and the other more dynamic, box-to-box. Toko probably will do...
Toko and Ince are the best suited, but I'm of the view that all six of our current midfielders (Toko, Ince, Crofts, Stephens, JFC and Kemy) could play the defensive role in a 4-2-3-1 formation.