"The fully-boxed chassis, we’re told is specific to this application, though some items, such as suspension bits are shared with the full-size Titan pickup"
http://www.autoguide.com/manufacturer/nissan/2012-nissan-nv-review-1578.html
I agree. The problem with speaking to dealers and marketing is they only care about selling what they now offer. I don't know anyone other than that to contact.
from my email to head office:
"At this time, we have no information about plans to introduce an extended cab version of the NV line up in the near future."
(doesn't mean one won't be released tomorrow though)