[source: emu_kidid @ gc-forever.com] Swiss as a bootloader on the Wiikey Fusion can be implemented as two different methods: Skip the IPL, boot directly to Swiss (custom "apploader"). Appear as a disc in the IPL just like the current menu. Currently, I've written (ported from the official flasher) some code to do the flashing and it seems to work well as it's giving me back valid responses but I believe the file I'm flashing may be in the wrong format (layout). This is what I've done so far: I took a known "flash" file and injected my own DOL into it. I then flashed the entire file. The IPL with the wiikey was telling me "Please insert a GC disc" and the Wiikey was generally unresponsive. Luckily the next time I tried to flash, the recovery kicked in and took over, resulting in a working chip again (or I could've just run the official updater again).
Note: These bootloader methods are developed with GameCube in mind as target console, using this impressive hack to load game ISO files from SD card. Thanks goes to emu_kidid for the heads up.