No security? The network is connected to the internet with NAT which goes through a gateway that has a VPN. Is that not security? There is no way to spy or track or identify a single user of the network. In addition you can also encrypt the wi-fi signal. Centralized ISP's are not secure. Centralized ISP's are the security breach themselves. The intelligence community gathers data through the centralized ISP's. They can now without any permission or warrant get your entire browsing history.
https://en.wikipedia.org/wiki/Network_address_translationLets imagine you have a place to VPN to that you trust and we ignore the fact that this destination is effectively a centralized ISP and that the logical party to operate a VPN endpoint for you is an intelligence agency. Ok. You can VPN to that place over a mesh or over a centralized ISP and then you get the same security and privacy properties as if you VPNed to it over some mesh.
You get the bonus property that any clown with a rpi cant totally shut down your network connectivity as they currently could with the mesh.
VPM isn't necessary. NAT also modifies the IP information. It's not a centralized ISP. It's a gateway. In a mesh network each node becomes its own ISP basically. You don't register to the gateway and pay a regular fee to the gateways as you do with ISP's. It does not have you billing data tied to your iP address. The centralized ISP's might have your crypto wallet data too. We don't even know all the things they gather there. Freifunk uses church towers for gateway antennas because they are both in very central high locations in cities and it's quite easy to convince reverends and pastors that the internet is the "anti-christ system" and that's why this is necessary.