The key to my statement, was traction aids, the terrain response system, as I understand it anyway, is a little more complicated than just traction control..... but thinking about perhaps that is overcomplicating it.....
Begs the question then, why has no-one developed one? Fitting an aftermarket diff-lock would almost certainly void any warranty (a scary prospect in a D3) but there are more and more around that are out of warranty and being bought by serious off-roaders keen to modify the vehicles......
That said, one has to get into some pretty tricky sticky situations before one needs a diff lock in a D3……..

