Horizontal shock absorbers for sway control.

That wouldn't be because the caravans wheels have been generally moved rearward? I reckon that may have more than a little bit to do with the improved stability.
Cheers
Disco

Probably, along with a few other improvements in suspensions I guess.

Thanks for your comments Tom...I was after thoughts on the engineering side of a simple anti sway device. I am a professional truck driver and have considerable towing experience..both at work and with my previous vans.
I do know the estimated unladen TB weight of my reputable new van...and expect it to be around 200kg max when near the vans ATM.
Have you any thoughts on my idea for a simple easy mounted anti sway device which I think will not need to be disconnected when off road etc as it will not impose large forces on the draw bar/tow hitch etc..nor will it hang low and be an obstruction when negotiating spoon drains, kerbs etc. I do wonder if the shockies would have sufficient travel particularly when backing/maneuvering.

To many people's horror or utter disbelief the simplest anti sway device you can use is to have the correct tow vehicle in the first place and don't tow up to the max of the vehicle give yourself a reasonable safety margin which brings the load closer to the weight of the tow vehicle, load your van correctly use the correct suspension to support any additional weight that is added to the van and tow vehicle making sure the whole setup "sits level" when loaded ready for a trip. Then you will not need to use these band aid type of towing aids wdh etc. It's your choice though but as far as towing aids go a semi can hitch up a loaded trailer which may weigh for arguments sake say 20 or 30 tons without any extra towing aids and using one pivot point just like your car, van does and drive safely down the hwy just something to think about especially if like myself you are a professional truck driver and that has been happening for probably longer than vans have been around for.

Totally agree with what you're saying Batt's.
What got me thinking about WDH's and anti sway devices was when I looked at the Andersen WDH which uses chains and a compressible nolathene? collar. It is also claimed to have anti sway properties and I have no reason to doubt that.
It then occurred to me that a couple of shockies acting in tandem or opposed, mounted in parallel to the drawbar could do the same anti sway job and would have simple mounts. I appreciate the comments on towing aids etc etc....but it's not really the core of my conjectures . I'm just floating an idea and hoping someone will come up with an obvious or arcane reason why what I think is a simple system wouldn't work.

Agree Johns advice.

You said you will have ESC fitted to your van, ESC is from my personal experience a sensible inclusion to most larger vans, I have experienced the rapid deployment of the ALKO ESC braking system when the sensors detect certain movement. However, ESC must not be relied upon to control yaw/sway, the critical bit is similar to trucking, ensure fully laden Van has load/weight in correct proportion/location and establish tow ball mass. Then where neccesary transfer required amount of weight back to front wheels so as to maintain steeering etc.

Whilst WDH are a pain at times, they are a tried and proven method of maintaining a safe handling rig, provided van is designed right and loaded correctly and vehicle is not overly weighed down at rear, then probability of sway/yaw significantly reduced.

For clarity, my personal experience with the ALKO ESC rapid deployment was not from usual sway, rather it was when right hand tandem wheels rode over an object at 70 plus kph and kicked my 3.4tonne 22 footer around.
Good vanning
Bob

See also http://www.withoutahitch.com.au/caravan/top-five-caravan-myths-busted/