Is it possible to put WRT-DD type firmware on any currently available AP box to cause the box to act as if it were a receive station/access point? A Google of a thread from a year or two* ago seemed to imply that v4 of the WRT54G was the last hardware revision that could support something like DD-WRT. The DD-WRT page seems to imply that v8 is now supported...*thread titled "WRT45G as receiver, simplest setup".
Apparently, the chipsets support "client mode", and having the 802.11 interface be the default route/backhaul out seems to be a matter of configuring routing/NAT/what have you.
For whatever reason, 802.11 PCI NIC cards and the USB thumb adapters seem to run about the same price as the AP boxes these days, and a 4 or five port Ethernet switch is included with the AP box.
-- Les Cargill