Guaranteed, someone will do that.I was just thinking a couple of MC bags could be mounted to the sides.
I'll have to say, one of the possible designs, may well be the best on tradeoffs of cost, efficiency and safety. A very light weight side-car saddle bag. Left and right actually. Use together or single. Bit tricky on the driver door side. Many people would get used to using the right-side only at times.
No added roll-over and no jack-knifing that a trailer could do. And this can be relatively inexpensive and easy to design for DIY.
It does implement a wheel/suspension as added complexity, but it's a good tradeoff to the other issues.
No other vehicle would suit this exact kind of accessory, it's unique to 2F1R trikes. In fact, AFAIK, I'm maybe the only person who has looked into that.
That does put the task on me to draw one up. I'll have do that soon. And there are two distinct types, solid bolt-on and articulated.