@audyssey. I actually missed the dual band in the spec, that's big as far as the radio issue goes.
The exercise was trivial, now knowing what I know. The only real thing you need to know that is not there is how to format the device (FAT32). Also not clear is that once you power on the device is that you connect by the wireless, not Ethernet. After you enter the first string, just wait for the prompt. After the second I think it rebooted, but you will see a notification that the connection is lost.
(none) login: admin
BusyBox v1.12.1 (2014-09-18 09:46:08 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.
# mtd_write write /media/USB1/openwrt-ramips-mt7620n-mlwg2-squashfs-sysupgrade.bin KernelA
Unlocking KernelA ...
Writing from /media/USB1/openwrt-ramips-mt7620n-mlwg2-squashfs-sysupgrade.bin to KernelA ... [w]
# mtd_write -r write /media/USB1/openwrt-ramips-mt7620n-mlwg2-squashfs-sysupgrade.bin KernelB
Unlocking KernelB ...
Writing from /media/USB1/openwrt-ramips-mt7620n-mlwg2-squashfs-sysupgrade.bin to KernelB ... [e]
The little 0 byte file is the piece that gets you into the shell. Before running the two commands to install OpenWrt you can query the existing OS if you like. Probably worth capturing dmesg and compare to wiki.
Regarding BB, that is what you are installing from ldpinney zip file. What I am not clear on is if I can reload it. I just upgraded from the GUI directly to 15.05, but probably should have poked around a bit. I know there are mount points included in the BB and they are not in CC. When you upgrade, can you please save a list of the packages installed in the delivered file from the zip. I just copy and paste the System=> Software tab to a text file.
I have been using the d.wonderful code on another device with a button action, and it's great. The lack of button control is a problem (not a big one but...) most of the time I end up in the same place, and as written in the code always requires making a new connection. Using the button action I can keep the last AP(STAtion) and reset on demand. Unfortunately not an option for this device.
I am now testing this code https://forum.openwrt.org/viewtopic.php?id=43352. As written it does not address the missing WWAN, but I have made some changes that seem to cover this. I am testing and need a few days to pull it together. This code is big in my mind, as it will auto config the WWAN side from a defined list of AP(STAtions)