Yes, I did see your thread on the travel case/trailer, and have seen/considered the idea in the past as well. It certainly is one viable solution, but wouldn't work for how I like to bike tour due to the additional carry weight/bulk, time to fold/unfold, and even ride/handling/maneuverability (unsprung weight, multi-track wheels, overall length). The only soft case that wouldn't significantly impair my ultra-light/-compact status (I self-supported tour out of the single T-Bag with a BPW [before food/water] of ~14 lbs) is the IKEA Dimpa bag, but you'd still need to virtually build a cardboard box around the inside anyway... and I think that's also the case for most soft case bags.

I am admitted extreme on the ultra- portability/compactness thing, both here and in the touring sub-forum, but it opens up some really neat options with my entire rig like: baby-strolling through museums, hiking 1/4 mile into the woods for stealth camping, climbing a 30-story staircase, and occupying only a single train/bus/car seat. CLICKY

Yes, I've seen videos of folks cutting the bordo and it seems to me that you generally need a 3 foot bolt cutter (or angle grinder of course) - I accept that risk for the compactness and that there's an ideal spot for it on the Brompton that does not impact the fold. Course, folding and wheeling inside is usually the answer in more worrisome spots. Hehe, as another example, I even use a vintage-style hairnet helmet because it folds tiny, and can be clipped to the bike, also without impairing folded size .