Apparently, HTC has made a custom version of the One for Chinese carriers and KDDI is using it. This suggests that Carriers have significant influence with phone makers.
I think expandable memory is extremely important although I disagree with the Engadget author's statement that microSD is "arguably more important". I think it's important to have some "minimum" amount of built-in storage (probably 32GB instead of 16GB) since latest versions of Android make it difficult to install apps and app data on SD storage.
"These days, the presence of a microSD slot on new handsets is arguably more important than the amount of storage on the inside. One such slot found its way onto the Chinese variants of HTC's One, and now Japanese network KDDI has unveiled its model -- the HTC J One (aka HTL22) -- also with expandable memory on the spec sheet (up to 64GB cards supported)..."
Also, FWIW, I believe KDDI is a CDMA carrier (I know my CDMA only VZW phones automatically roam onto KDDI when I visit Japan -- I don't need to rent a local phone). So, it looks like a CDMA version of HTC One exists. Of course this doesn't stretch one's imagination too much considering the 'DNA is already very similar to HTC J Butterfly and HTC One in terms of radio capability (although the 'One is a smaller form factor ).