Homebrew GBA link cable simulator?

[Grink]

would it be possible to create something like this that would simulate the gba's link cable? i just don't want to have to manually input passwords into golden sun 2

 

[bendevnull]

GBA VC? No. Definitely not.
mGBA or some other GBA emulator? Possibly. Talk to the emulator dev about that one.

GBA VC can't use link cable functionality because the GBA VC isn't an emulator. It runs, in non-technical terms, on a GBA that is inside of your 3DS. Therefore, it doesn't have access to the wireless capabilities of the 3DS, so the link cable cannot be simulated in GBA VC at all.