A very (very) long time ago I saw black and white film (perhaps British MOD in-house documentary stuff) showing a 'military' Land Rover climbing a steep hill towing a trailer on which was a one and half ton block of army-issue concrete! So impressive!
It seems that this was achieved by means of a drive shaft somehow taking torque from the LR rear axle to power the axle of the trailer. This suggests that the LR was not actually 'towing' the trailer but, perhaps, being pushed up the hill by the trailer. On insecure terrain the wheels of the trailer - with its hefty load - may actually have had more traction than the lightweight LR itself.
I saw this around 55 years ago, was so impressed by it, yet have never seen this principle used since that time. Yes, for hill climbing it would demand that a low enough gear ratio would need to be available (the Land Rover was never renowned for its engine power -in Australia all had to be fitted with a proper size Holden engine the mountings of which exactly matched the original engines) and, yes, it would involve the attachment of the extra drive shaft when fitting the trailer to the back. But for the sake of ensuring that wheel sizes matched all round etc. and for a few extra minutes to bolt a uni-joint together, this would surely provide a great increase of capability?
Perhaps this has been tried since then? Have I happened to miss that?
J.Clifford. Victoria. Australia.