Holy shit I love this!
B_rob successfully recreated and got one to work. Also Funnyplaying did a while ago.
Those caps you circled are 1uF X2Y caps. The filters are ~150mOhm ferrite beads
Try holding X+Y+Z and then power on your wii (keep holding for a second). This boots the gc+ in safe mode and you should be able to try the update process again
What do you mean that you can't boot the installer from the settings? It should boot. Anyways you also try booting into the safe menu (holding L+R+Z) while booting. After the bootloader text it should boot into the safe menu and you can boot the installer from there