My experience with adjustable shocks is they are more trouble than they are worth.
I also think there is no way you will get a "much softer ride", improved yes but by a large amount, no.

Try for air suspension such as http://www.airbagworld.com.au/airbag...sion-kit-.html.

I think you will have a better case to argue and get a much better result and use the Seat and Shocks as a fall back position