I bought the fibreglass materials to make my own one-piece t-top replacement. I would use the existing tops in-situ as the former to get the shape. I liked the idea of a lightweight top for security and basic weather protection when parked, so that I could drive the car topless and leave the heavy and bulky tops at home. It would need to be secure for driving home in the wet so that it didn’t fly off and decapitate the public. I haven’t gone ahead yet due to the issue of carrying it on, or in, the car. If placed behind the seats it would interfere with the seat belts. If fitted to my luggage rack then a bit ugly. Otherwise, make it in two pieces for ease of internal storage. Two pieces not as strong, simple, or weatherproof but still lighter and less space consuming than the originals though.
Benefits seem a bit marginal.