A big disadvantage of a lightweight wireless community intranet is it’s limited range. A possible solution to this is mesh networking.
Mesh networking is when nodes on a network forward traffic on to other nodes. This means that each meshed node serves to extend the effective range of the network. A meshed network of devices such as a Raspberry Pi or OpenWrt routers can extend a smaller wireless network to cover a larger area than could be covered by the devices alone.
One open source modern mesh networking protocol is called ‘better approach to mobile ad-hoc networking’ or B.A.T.M.A.N. This protocol can be integrated into a PirateBox installation and used to extend the available network.
A cautionary note! Remember that the mesh network will still rely on your modestly powered server running on a OpenWrt or Raspberry Pi. If you expand the area your network covers you will invite more users. This might overload your small server.