Just make a memory card interface that is compatible with the most common memory cards already. This will increase the value of the Core system immensely, and could certainly help in Asia. A game that requires storage could even be bundles with a cheap memory card.
Now they just have to do something with the Core. Add a wireless controller instead of wired, and drop the price on the 20gb HDD to $60 and they would be setup for a great Xmas in north america.
I think there are better options. All that would do is remove the option of buying a HDD for core users, and push them towards using a MC instead. May as well leave that choice open, especially to push online penetration.
$15 memory card with a $60 HDD is so damn obvious, I don't know what MS is thinking.