It makes sense technically, but I don't know if it is practical.
So the 5500 SD control chip is closed and useless, well do we even need it in the first place?
The Linksys WRT54g router has mmc support hacked in, and it has no special chip for that, just gpios http://kiel.kool.dk/
So what if the normal SL-5500 slot was used for this hack, and gpios were stolen from the SD chip? Maybe the power to that POS could even be cut off at the same time.