Remember BMW and LR worked together for a while and stuck some BMW engines into LRs - although I think these were only petrol 2.8l engines. Funnily enough this has gone quiet in recent years.
Nissan tried sticking its 3l TD engine into Patrols with spectacular results for the wrong reasons (they went pop!) - yes, the Nissan engine was unsophisticated by BMW standards and I think it was also a 4 cyl rather than 6 cyl. For my money, heavy duty 4x4s like LCs, Patrols etc need fairly large capacity engines as these give more grunt at the bottom end of the rev range, despite the torque figures on paper suggesting that the high output smaller engines are superior. The larger engines are also relatively unstressed, so longevity is greater.
More power sounds nice but how does these high output BMW engines cope with a bit of dust entering them? Or water in the electronics? Or a bit of muck in the fuel going through their fancy injectors? What about the shock loading on the already-stressed crank from a spinning drivetrain on a heavy truck that suddenly gets grip?
This is where Toyota's approach differs from BMW and others - Toyota is shooting for reliability and longevity at the expense of performance and efficiency. BMW has the opposite priorities.
Progress is inevitable and gradually these trucks will be re-engineered to use these more efficient engines without breaking anything. I guess the passenger car market is way bigger than the SUV/utility market, so car manufacturers are likely to show a bias towards the larger markets. We should be grateful that Toyota has stuck to designing a suitable utility vehilce for ours needs/desires for as long as it has
Or we'd all be driving pimped X5s or LRs