Update: HTC tells us that this particular surgery's a risky one, not only for your warranty but the connectivity of your phone. Here's what you're getting yourself into, according to a senior company rep:
While this is not technically impossible, one thing that is important to know is that the process of removing the cover to access these components is actually very tricky – and in many cases, will result in the antenna section being irreparably detached from the circuit board (rendering the phone unusable). Additionally, to actually replace the card, a few reasonably important parts have to be forcibly removed. So, just a good warning to anyone thinking of attempting this maneuver is that the possibility of bricking is extremely high, and will, of course, void the product warranty.Update 2: But if you do throw caution to the wind, you may be able to get it to work with a 32GB card.