If going the Super Game Boy route is out, I'd still be interested if they ever make a standalone Game Boy Advance console. Especially if an option for original aspect ratio and using Y & B was provided, S-Video or perhaps even component out was present, and they didn't limit the user to using a controller included with the device since I'd want to use something like an original SuperNes controller.
Of course my GameCube with Game Boy Player already does that since the disc never leaves the drive, but the concept grabs me enough where I'd want to check it out where as this halfway approach they did here just turns me off unlike if it was a full GBA equivalent of the Super Game Boy or a full console.
Were they running on a Game Boy emulator running off the GBA hardware? I presume so since I think it was you that told me that there wasn't a dedicated GB/GBC flash cart a few years ago.