Im personally not too knowledgable with this but over at GBA Temp theres news of a loader that runs from an SD Card, I don't condone piracy but its an interesting release none the less:

Thanks to the work of ahezard, Gericom, Apache, Robz8, _catcatcat, and shutterbug2000, we can now load NDS games from the SD card, without any flashcard/SLOT-1 card.

As promised, a release is here, on Christmas/Christmas Eve.

Don't expect high compatibility or save support yet, but do expect many, many updates.

However...:
shutterbug2000 said:
A fair warning and note to all: If you don't wish to save, keep ALL cards out of SLOT-1. THE SAVES WILL BE OVERWRITTEN IF THE SAVE CHIP MATCHES.

For example, running MKDS with an AC:WW game in SLOT-1 will overwrite AC:WW's save, since the chip is the same.

However, if you wish to save like this, TWLSaveTool can tell you the chip type. Just backup the old save first.
Click to expand...
Have fun!

Some games that work well with this version:

Warioware: Touched
Mario Kart DS (if you have a physical MKDS card for saving)
Bomberman
GoldenEye: Rogue Agent
Space Invaders DS
MegaMan ZX
Yoshi Touch & Go

Release Page link --> https://github.com/ahezard/nds-bootstrap/releases

source