The next thing I'm interested in is trying to get different voltages out of it; if I can tweak the standby line to output 1.9v, then this'll be great for testing gamecubes and N64s as well.
For regulators from the 40, its pretty unlikely there is a simple way they can be tweaked to output anything lower than 3.3v. Here is the datasheet for the linear regulator.
Linear regs can output a higher voltage than their stock voltage, but not a lower one.
For the regulators on the 60+, I wasn't able to find find the datasheet for the standby line. I haven't looked too much into it though. I pretty sure it uses a switching regulator instead of a linear. It should be possible if you change some resistor values, but without the datasheet I can't know for sure. Maybe hook a pot up to the feedback pin and adjust until it reaches your desired voltage? Not sure which pin is feedback though...
No. These are just the standard Wii regulators, removed from the board and made to work again(minus the safety features.) They serve no purpose for anything other than testing. Retaining them is quite nice if you want to work on the trim, and don't have custom regulators or adjustable power supplies available.
I'm pimping mine out with LEDs so I can always verify that I've got power coming out of all 4 lines.