Is it possible for there to be an unlocked Nexus with LTE?

Is the reason why the LG nexus doesn't include LTE because it is a closed technology? For instance could Google make an unlocked pentaband nexus with all US GSM frequencies and then include an LTE radio with the exact 700MHZ band and frequency that AT&T runs their LTE network on? With Verizon still running voice over CDMA I think they still have a strong hold over what phones can operate on their network, but is AT&T doing the exact opposite of what make GSM so great and actually blocking access to "unauthorized" devices on their LTE network? I haven't heard much commotion about this subject.