I'm aware, but the 17" is just too huge. The 15" is just right, and I wouldn't mind it being larger, as in previous generations, if only from squarer corners.

I'm not convinced there's an issue of space per se, since the SD card slot is only slightly smaller, and, even there, a card is not completely contained within the chassis when plugged in. Doing this with ExpressCard would be better than having none at all, IMO.