Turn the trailer as a motorcycle trailer + green license plate

Can you give me an overview of the legal side. I want to strip an HP350 possibly an HP400 (loads to 350kg due to the vehicle) on the base frame and equip it with 1 rail. The whole should then run as a recreational trailer tax- and insurance exempt with green registration plate. ——————— Conversion+loading should not be the topic. What about the green registration plate? Can I get this so easy? What does the Sunday driving ban say? Have too many vers red stuff read in connection with the green license plate. 100kg registration with an unsprung trailer only with XX fraction of the unladen mass of the train vehicle??? What if the track survives with the motorcycle at the rear? Change in length of the trailer possible?