Actually having hardware lying around to reverse engineer is the limiting factor for me. I suppose I could give it a shot if people who own the devices sent me the required data. I'd need their help with testing.

USB stuff was really nice to work with. Wireshark made it really easy to intercept the control commands. For example, to configure my keyboard's RGB LEDs I need to send 0xCC01llrrggbb7f over the USB control channel; the ll identifies the LED and rrggbb sets the color. Given this sort of data it's a simple matter to make a program to send it.

Reverse engineering ACPI stuff seems to be more involved. I wasn't able to intercept communications on the Windows side. On Linux I managed to dump DSDT tables and decompile WMI methods but that just gave me stub code. If there's anything in there it must be somehow hidden. I'm hoping someone more experienced will provide some pointers in this thread.