I am looking to buy a hard case for my concert uke so I can take it on the plane with me over Thanksgiving. The Kala Uke Crazy cases are good quality, they come with loops and a strap, and even a hydrometer, but they do not have an arched top. I'm very paranoid that the airline may hand over my uke to their gorillas at the gate. (Alaska/Verizon flight -- small plane. They've taken my carry-on before.) So I want an arched top. The Oahu cases are very nice, I think I'm going to order one of those. I was thinking about taking it to the shoe repair guy to rivet on some loops for straps. Then I searched the forum, and found this thread.
It's funny I didn't even think about just putting the lower bout of the case in a small day pack, zipping it up each side, and carrying it that way. I'm still intrigued by what you described. For that matter, if someone could sew they could just make a form-fitting bag with straps to carry it in. I'd buy one of those.