A fascinating idea, I wish you a lot of luck in this endeavor! If I were going to go this route, that is, to engineer a network not dependent on the Internet -- I'd first go down to the most fundamental principle of WiFi, Bluetooth, ZigBee, EDGE, EVDO, LTE, etc. -- and that most fundamental principal is RADIO . From there, I'd ask the question -- how can any device which implements one or more of the wireless protoco…
SDR became wildly popular (well, relatively, amongst geeks) when someone worked out a ~$10 usb dtv tuner could be used easily as an SDR receiver. There are very few (but not zero) rules around recieving radio signals.
Once you start transmitting though, things get way moire complicated very quickly. Some of those radio protocols you listed (Bluetooth/WiFi/ZigBee) typically use "ISM" radio bands, where the rules are less stringent (but there are still rules), some of the protocols you mention (EDGE/EVDO/LTE) will very quickly get you found/shutdown/fined if you start transmitting on them. Telco's pay millions for the licenses to those bands, and strongly protect their exclusive use of them.
If you "just use" your wifi/bluetooth radios as they were designed, you'll be complying with all the regulations (including things like ensuring you abide by geographically different available channels, 2.4GHz channel 14 and sometime 13 and 12 are not available depending on where in the world you are: https://en.wikipedia.org/wiki/List_of_WLAN_channels#2.4_GHz_... )
If you start screwing around at a low enough level to be controlling the radios without the higher level drivers - you become responsible for all the global regulatory shitstorms you might bump into. While that would be a fun thing to play with (and I say this as someone who's used a USB VGA dongle as an "SDR Transmitter" in ways that are _totally_ not legal where I live), it's not really a sensible path to go down if your goal is widely usable decentralised non-internet connected messaging.