I did that some time ago in a simple-minded fashion, but I've had to revise my layout somewhat. I had an ext3 partition solely for /usr/portage, and it was mounted on that node, but every emerge --sync deleted the /lost+found directory. I don't know how serious that is, but of course no-one likes to have damaged file systems on their boxes, so I used tune2fs -c to set the mount count to 1 so that it was repaired every time the box booted, but that was taking too long and it was only a palliative anyway. The solution was easy, though of course I didn't see it at first! I only had to point /usr/portage to /usr-bits/portage (/usr-bits being the mount point of the partition) instead of mounting the partition directly in place.
chattr +i /lost+found would have probably worked -- [email protected] mailing list
