I believe there was a company trying to develop/sell a "backup" system similar to what you describe. It didn't catch on, and I think there is a reason why!!

That said, installing a compressor is very handy. I have one mounted in one of my rear cubbies. Helps a lot for airing back up and such. As for the EAS, if you know your compressor is going ****, you can just air up one more time and then pull fuses.

 

The exhaust valve is a non-issue I suspect. On another vehicle I owned there was a mod to install an exhaust valve in a new location to prevent exhausting air back through the dryer, which can cause issues. A second benefit was that the system exhausted a lot faster resulting in quicker lowering - although the LR3 is pretty quick already. Anyway, the exhaust port is a just a solenoid valve opened on command. So it could easily be separated from the compressor and installed inline where needed.

The other car was a Mark VIII and the valve setup was called a spider valve because it was inline with the four airlines to each bag, thus looked like a spider. Google can bring up pics, etc.

Going back to what others have said, it seems the Rover system is a bit of a pain. I know there are software updates to help compressor issues on some early models. Or switching brands can be an issues at times from what I read. You would think it would be a simple computer/relay driving system but it seems more than that.

 

Have a look at this Aussie site and the EAS inflation kits, wouldn't be too hard to make up something similar from local suppliers.

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