While I would really be quite happy for someone to prove me wrong on this, as it might open up possibilities for my HTPC at home, pretty sure this isn't going to be possible without some warranty voiding modifications to the hardware. I looked into this idea for desktops, for my HTPC, and basically it amounted to having to splice something off the standby power line from the PSU. So the issue is largely going to be that the USB ports are unpowered until the unit starts booting, and you'd have to alter that internally, which would be a really cool hardware hack, but also warranty voiding. Again, I really do hope someone can prove me wrong on this, but I'm not going to hold out a lot of hope on that.