A reduced hilt is just that: "reduced". If you add the extended size and weight of the much larger squared top the knife would be out of proportion and require an unusually cut piece of hilt material. For "all of the above" the shop will tend to "just say no". "Could" they do it? Sure. I wouldn't take the order as I can't face rejection by Valerie...and I would be facing it, in the case of this knife.
May I ask..."WHY"? Do you simply want something that nobody has ever seen before, or is there some other reason? You can order a nickel silver "single" hilt and have it "squared"...
Best, Capt. Chris