So I came up with this little app for both gamecube and wii which can send over gb and gbc roms to a gba using the link cable! This all works thanks to Goomba v2.30 which is a really nice and small gameboy emulator.
Ready-to-use dol files are right over here. All you have to do really is have a "roms" folder with gb/gbc files on your sd gecko on gc or sd/usb device on wii. The gba has to be in port 2. Also please note that because this all gets put into the gba ram the max file size including the goomba gba (42.4kb) is 256kb.
Source code wise there is not a whole lot happening but if you want to check it out its on github as well.
Enjoy playing some classic gameboy games with the help of the old gba link cable

See it in action with the game boy player: