I think the likes of SDC, Tiger, Cartwright are mostly set-up to build trailers for the large distribution operations, built to a price, not for longevity, this isn’t to say if you paid the money for something else they couldn’t do it, but it not their bread and butter work.
There are specialist chassis makers who work on small volume jobs made to the customer specification, the chassis for the race trailers we get are made by Weightmaster Trailer in Scunthorpe, obviously I can’t say if they’d make a trailer to fit your requirements, but might be another option to look at.