Manually set transform on certain bones in skinnedmeshrenderer

I have an animated model and I'd like to make the character be able to point in any given direction (maybe using something like transform.forward).

What I've done is created an arm outstretched 'animation' to the model and applied a mixingtransform to the arm so I can play any animation and then play the 'point' animation so whatever his animation is he can point.

The issue is that he only points forwards and despite trying to add rotations to the root arm transform nothing works, the skinned mesh renderer seems to outrank it.

So any ideas how I can do this?