Try to modify Megaman Zero Collection. That has 4 GBA roms in it. The fact that the original screen resolution for it leads me to believe that the roms are in there somewhere, and interchangable. And Post stuff like this in TECHNICAL HELP.
I don't know...I only thought that they ported it to the DS... I'll look into it. EDIT. I can't find specifics as of yet, but I found a video of some guy saying he ripped the Sonic roms from the NDS rom and is playing them via JenesisDS. - http://www.youtube.com/watch?v=1r7FQGXx-Rs
If MMZC was ported, why wasn't it scaled up to the DS' Screen? GBA and DS code can't be the same, and they couldn't release the collection using GBA slot mechanics for loading because the DSi didn't have a GBA slot. Heck, Metal Slug XX got up-ported to the PSP from 7, so is the source code compatible with other consoles? edit By GBA slot I meant using the GBA hardware in the DS to run the titles.
Not that I know of, but there are probably homebrew emulators that play GBA roms. ...The DS can play GBA games anyway, which usually aren't very expensive to buy. So why not just buy them?