Cheese nailed it. It's a heavily modified gamecube heatsink. I'm actually going to be making another one today, currently rigging up an entirely new metalworking setup so it's not as much of a pain in the ass to do a bunch of heatsinks.
The larger 5v reg is for compatibility with the HDD adapter. I haven't really set up to completely test the AMS1117's capability yet. I'm only using two different USB devices, and it's only been tested with my card reader. Off the bat I'd say it most likely works perfectly fine for normal flash drives and other USB devices. It might also work with some additional components, because I'm currently using none.
Using a single PTH08080 reg for the 1v and 1.15v lines hasn't been properly tested yet either. The only thing confirmed is that the Wii will boot to the sysmenu...but that's not enough to say it works. You've gotta test everything, and currently nobody has a setup that can do that in our expected environment except me. Additionally, the math puts it too close for me to comfortably do it for commissions, especially because of the lack of complete and proper documentation on the Wii's power draws.
Yes there is a regulator you could probably use, but it's extra dumb to do that, because not only does that regulator get hot, but there's no advantage to running them both off of the same voltage line in that case other than size, which is negligible considering how the world's smallest Wii can currently comfortably fit 4 regulators, plus the MX chip with room leftover.