A 4MB flash, 16MB ram version of this (same chipset) is already freely available for $15 as module (1), or $26 with a break-out board (2). You get 2xserial, a bunch of free GPIO's, 2xethernet, i2c, usb. OpenWRT has already been ported to this module, although you need to really strip it down to make it work reliably given the small amount of ram.
1) http://www.dx.com/p/hi-link-hlk-rm04-serial-port-ethernet-wi...
2) http://www.dx.com/p/hlk-vrm04-multifunction-uart-serial-port...