Oh the collection that never was, I die a little inside every time I see this.
MegaMan Mania, the complimentary collection to the Anniversary Collection, would have compiled all the GameBoy titles into one convenient GBA cartridge. After countless delays, the project was canceled due to the "misplacement" of the original source code. Regardless, MM Mania producer once stated the collection would make the jump to the Nintendo DS instead, but we've yet to see anything come of it. Sad, sad, sad.