What about using LPWAN technology such as Sigfox? You don't need to create a mesh network anymore (expensive to do, always some gateways that needs to be fixed, and pairing configuration & issues). With Sigfox, assume the network is already here (you can check current coverage at thinxtra.com/coverage), the device connects directly (no pairing) via Sigfox to your cloud. Happy to discuss further at email@example.com
Excellent article on energy harvesting. With LPWAN technology, devices only consume very little energy, thus making it even more possible to use simple & cheap energy harvesting solution to power them for a much longer period. Kinetic & solar might be the most easy ones to implement. As millions of IoT battery powered devices will be deployed, we have to start using now those energy harvesting solutions to minimise the usage and the size of polluting batteries. Something Thinxtra is very focus on.