I've read through both of those threads, the one I posted and the second one posted above. Unfortunately they both went the route of replacing the existing antennas with wires or external connections. The closest one to my idea was this:
Originally Posted by Lock-N-Load
Really though, in the end, it seems if someone wanted to get really hardcore, they could dremel a slice out of the back that is tall yet narrow, go to home depot and get some plexiglass, sand it down to obscure the view into the device, and epoxy that in place and place the wire into that as a window. Totally possible IF you wanted to kick it up a few levels now that the hard work is done and shows an antenna wire can hep. Essentially steal Apples' idea but keep it simple and make it home grown.
Like I said, slicing off the top of the back and covering it with plexiglass is probably too much. I'm thinking more like just a hole, over the existing antennas, covering it with epoxy, and making a Wifi Window like that on an iPod Touch:
Tmobile USA - HTC AMAZE (stock)
SD Card - 32 GB class 10
Asus Transformer T201 w/ Dock.
ROM: Flavor of the week.