Sorry for late news but I was formatting my PC.
Well a patcher for ds games has been released to patch DS games to load from any GBA cart. A great step forward in the DS scene, although you still have to use the QPC method. It also trims the roms, for faster loading.
Quote from readme - "This program will patch a normal (ie. not a GST release) rom to allow it to load from a GBA flash cart instead of the usual NDS card. It also attempts to patch the saving functions so that it can save on the flash cart's SRAM instead of using the NDS card's SRAM."
I have tested this myself and I am currently uploading the zip file on Filefront so everyone can download it.
Hope you enjoy it, I really am.
UPDATE: You do not need to have different ds carts for saving. I saved NintendoDogs with metroid demo in the DS slot, although I did not have a 2Mb gba save, it saved part of the data, but it works. I also tried NFS2DS and Ridge Racer, but they do not work.