Please take everything I write with caution, because I might have no idea where the fuck I'm talking about:
I believe that the CycloDS has ~2MB of internal memory. Where this internal firmware is stored/updated.
Now, does anybody knows if that piece of memory also covers the bootloader, that uses the exploit the get recognized as a NDS game?
If so, shouldn't it be possible to simply update the internal memory (and bootloader) with a DSi-compatible exploit, so that the card could be recognize by a DSi as well?
Just a dumb thought of mine, but yeah.