>>56541315File format conversions are the easy part, communication between the hardware is more up to Nintendo than any of the game devs and may actually not have been possible on the official hardware as released. The gba and older gb/c used different link cable pin-outs, not sure if gens 1 and 2 can even trade amongst themselves on the newer hardware I think it still requires an old cable if both games are plugged into a gba and I am one functional gba short of being able to test that myself, but if so they could have made trade/transfer to gen 3 work with the caveat that it required both games to be running on the newer hardware, though I can see them not being willing to support that kind of specific case even if it's technically possible just to reduce complaints from idiots not setting it up right. The gameboy player for the gamecube should have worked since it's essentially a gba with video out to the gamecube, though that would depend on box being able to replicate the boot disk to get it working, something I can see Nintendo not allowing even if Game Freak wanted to. Not sure if the gamecube to gba cable could have been used given the old carts were taller, I'd go check if the game and the cable can physically fit in the gba together but my cable is 3rd party so dimensions may be a bit off. In either case, once the hardware is talking to each other all they had to do was program the gen 3 games or box to read the older cart to figure out if it's gen 1 or gen 2 and the save file to get access to the pokemon, similar to the n64 transfer pak, and convert the old data structure to the new one same as any other transfer does - just gotta copy bits from one location to another and set defaults for new data that didn't exist in the old structure. I've seen at least one successful attempt at a custom cable/board to connect gen 2 and gen 3 and enable trading to work about the same as gen 1 to gen 2 did.
