Ah, Jurgen is still alive... I will be very happy about constructions of your improved model like your others.
My favourite improvements, I would make (if I had enough time an ability):
extension to 6 axles (5 with steering, 2 only driven
corresponding to this extension of the boom
boom mounted to the back - this should be possible with a special actuator like this: http://www.bricklink.com/storeDetail.asp?b=-13197241&h=142678&catID=P36 and the video:
I know, the actuator is not for purists and ist not cheap but it offers more possibilities for such models. I don`t think, that TLG will offers us suchlike this in the future.