Motorola Droid 4 has LTE working only in North America only so adding support for more LTE bands in the face of plans of 2G network shutdowns and cutting down 3G bandwidth would be in my opinion a significant benefit.

As for Moto Z - it seems to be more a phablet than the average smartphone so having a bit smaller device (~5" ?) might encourage also those who do not prefer big devices.

The next alternative (not mentioned here) - Motorola Photon Q has built-in on motherboard SIM card so to use it out of USA Sprint needs soldering in the SIM slot which is not acceptable for many of the potential customers. LTE doesn't work outside of the North America too.

Beside that, newer Android versions are getting heavier and heavier so improvement in CPU/GPU/RAM would always be welcome for the potential consumers (even though the custom ROMs for the existing devices are still being released).

There seems to be some niche. Not sure how big, though.