Speaking of the X-Blade's design I'm surprised the fact that it was made up of two Kingdom Keys was never addressed. You'd think that would mean something in regards to Sora's Keyblade
I think initially Nomura was going to make the Kingdom Key and Kingdom Key D be something really important and integral in BBS which is why he went with the design he did with the X-Blade. Of course, BBS underwent major revisions early on and a lot of the plot changed, so what we ended up with was what we got.
It would be fair to believe that Nomura will probably eventually bring meaning to its design in relation to Sora later on in the future. We all know Nomura can't help himself when it comes to these kinds of details. This is the same man that pulled in old concepts from KH1 and Versus XIII (despite how much he tries to deny it), after all.