well maybe a Ford pump but ...
There is talk on some of the boards about a Ford pump for the Mark Trucks and the like that is physically mounting wise similar to the pump on the 3. The trouble is that it just seems to be talk.
If there is any problem with the air system, it is that Land Rover is about the only manufacturer to run the compressor at about 250 psig. Everyone else, including the semi trailer guys run at under 150 psig.
That is hence, the basic problem; no one, (including LR), knows how to build a reliable, (lasts at least 4 years until the warrenty runs out), pump that operates at about 250 psig.
Running and storing air in the tank at the high pressure has the advantage that when the truck lifts, it does not do the camel thing like the earlier Range Rovers - lifts first at the front and then the rear. There is sufficient air in the tank to do the lift on all four corners at the same time.
What is interesting is that the air springs still operate at the lower pressures, (about 100 psig), so you do not need much more pressure than that to actually function.
Some are installing a second air tank on the other side of the 3 to add to the stored air volume; with that done, then a lower air pressure compressor is practical, assuming you can override/reroute various software signals between the ECU and the factory compressor.
2005 LR3 HSE 4.4L V8 petrol; 18" x 10 spoke wheels; Traxide dual battery kit; Rear Cargo area LED lighting; PIAA 2500K H11 Yellow Ion fog light bulbs; Patch cellular antenna to underside of interior of glass roof; Air Suspension ECU Fuse 35P disconnect switch; CounterAct LT-2 capacitive corrosion control system; LLumar AIR80 Blue Low E clear Infra Red heat reducing side window tint; Manual upper rear door cable release; Schrader valve "air in" mod to OEM air tank; Akebono ceramic pads on OEM solid vented rotors.