I wonder how the RS4 thing works?
Could be some peltiers and a fan powered by solar/battery. Not as efficient as a compressor system but quite small and scalable.
Personally I would rather have electric compressors along with electric water pump and PAS. Yes having to generate more electricity seems to add more inefficiency into the system but electric means you only need them on when needed, you can have them running with the engine off and you can boost them independent of engine speed. It also does away with parasitic serpentine belts and tensioners and idlers and means you can put things in accessible places and free up room around the cambelt for access. As well as not taking out your cambelt when something fails (eg water pump).
The new peugeot/bmw turbo charged petrol engines use electric water pumps so the pump does not run when the engine is warming up and can continue pumping water when the engine is turned off.
Another benefit of electric items is they can be shut down easier when accelerating so instead of needing a 120hp engine you can get away with a 110hp engine for the same acceleration response. Small savings which are all helping push up MPG figures.
You can also reduce the engine electricity generation load by extracting more energy during braking which helps reduce brake wear (slightly) and utilises waste energy.
Some mechanical aircon systems do this already (the old peugeot 306 one does) in that the magnetic clutch releases during hard acceleration to free up engine power.