Well, it's sick to have / on a 256M disk. But it's still not a good idea to move vital parts of the system to a slower partition. And they reside in /usr (see libstdc++6)

I'd suggest moving / to /dev/mmcblk0. Altogether - we get rid of the problem of small rootfs. And we take the opposite of optification - we do nandification - move the vital parts of the system (libc6, libstdc++, glib, hildon) to NAND.

Beautiful, isn't it? We still get the blazing fast performance for vital components and we don't have any problems with full rootfs.

The only issue may be the boot process, but I don't know how big it will be. Generally, the boot components are usually vital.