There is absolutly nothing wrong with cloning a cab design, just as long as it isn't passed off as an original.
I'm in the process of building two of the old 66-67 Sentura II, 2 x 15 cabs which were 36 x 24 x 11.5. They were the ones with the 15's off set kattycorner from the center line of the cab. I had a 67 Sentura II with two of the originals which I had to sell many years ago. I've just purchased a 67 Seuntura II head and am building the cabs to go with it. I'm making improvements such as using 13 ply birch plywood with rabbet & dado joints, full length cleats at the corners, and I have 4 JBL K130's to put in them - 2 per cab. I got the nickle plated corners, and the handles - which look as close to the original as I've seen, and the rubber feet for the side from Parts Express. ( Parts-Express.com). Only problem is that no one makes the original Silver/black grill cloth that was used on the 67 models, so I may have to do it in the Fender Style cloth which is still available.
Rob