I spoke to Rita at Bike Revolution in Oregon. They make and supply the collapsible trailer for Bike Friday which works with their Samsonite hard case. . They will do custom trailers for the below sized hard case. So if you had a regular 26" wheeled bike with S&S couplers, you would not have to spend additional money on a Bike Friday. I rode a Bike Friday with case and trailer and really liked it. I never knew it was there. I liked the hitch and the two wheels when stopped. I did not ride over rough roads. It was nice not to have to worry about the bag. Below is a copy of the email response she sent back to me. Maybe it will help you.
From Subject Size Categories firstname.lastname@example.org
Re: Bike Trailler 26x26x10 Hard Case. 9 KB
Robert, thank you for your follow up. I checked in with the owner & Fabricator and the decision is... yes we can build a custom trailer for your hard case. Based on the wider wheel span & your described use it will need to be a heavy duty trailer
cost will br $ 249. + shipping
and completing would be estimated at 7 - 10 days from time of order.
Thank you for your interest let me know your decision Take care Rita