I tried this today with a TP-LINK TL-WR703N 20130703 but it looks like it bricked it. After the flash I couldn't connect to it at all. Also, unlike the routers in the Avalons or a Raspberry PI it required an external power supply to work but when I used it the Avalon wouldn't power up at all. Am I missing a hardware mod or something?
Was happily running 20130703 since release with no issues at all. Highly recommended (on 20 or so units - batch 1 and 2, on my batch 3's I just run stock because of the temp sensor change etc). I saw the new firmware and decided to give it a shot on a batch 1 and it bricked it. No reset or nothing could get it back.
I figured no problem. I picked up some extra TL-MR3020 to replace the TP-LINK TL-WR703N router but those didn't flash and in the end I gave up on messing with that (from what I can tell you need a custom one or something).
A retail TP-Link 703n can be found on eBay or Amazon for about $20. It can be flashed with the 20130703 firmware, and then plugged into the USB cable inside the Avalon. The LAN cable or WiFi can be used to access it. It has a mini-USB power cable. I ran a for-repair Avalon a few hours this way before I got the soldering iron and made a permanent repair.