Looks like the air box is at the front left corner for both petrols and the diesel
Looking in the front left corner of my CRD there doesn't seem to be much room behind the headlight to get an intake hose through the front left guard.
The CRD also has an electrical box just behind the air box that the petrols don't have (could also be a 2012 vs 2011 build difference). Front RHS is also a little different between the petrol and diesel
Looking in the engine bay and at the 3.6L V6 image it might be possible to come through the LH guard into the area at the bottom left of the windscreen and then come over the top of the shock tower. The petrols could possibly keep an airbox in the same place, but it would need to be redesigned (sort of turned upside down). The CRD would probably have to get rid of the air box, but would need decent filtering on the snorkel.
If you could get rid of the air box then you might be able to get a smallish 2nd battery under the bonnet.