It seems to me that the Pico-Light would be the ideal trailer - seeing as it is a sort-of teardrop replica of the Piccolo trailer towed by Isettas in the past.
Welcome to the Forum. I agree you need something unique! A friend of mine has an Isetta, and I have driven it. Not a lot of towing power there, so you will have to build light. Just saw some cool builds on the Forum last week from some 2CV meets. Check those out. Have you ever heard of an "Egg" saw a few around western Washington about 15 years ago. VERY LIGHT Good Roads Brian & Sandi