Keep in mind that AT has to keep production moving. So they really don't want to let something cool and then check/straighten it between each weld as that would drive costs way up. This will have an affect on warping the trailing arms during fabrication. By how much I do not know since I haven't been there.
I have some concerns over going too soft. Rider comfort isn't a concern (is it???), so a super soft and slinky suspension for a trailer isn't the order of the day. Soft enough to not shake up the beer or break the eggs is good enough.
That was really my thinking also. It would not be as soft as the AT suspension by any means, but it would be independent, so it wouldn't throw the trailer side to side over every rock. My trailer is probably heavier than a 416 and with the adjustability of the VW spring it could ride ok I think. I want to run 35's on the trailer for spares for the 40 and they have that shock in a 16" version that would probably be perfect for a near vertical shock.