Right. If you use ntfs3g.tcz (an extension), you get read/write access to any ntfs parition mounted after ntfs3g.tcz is loaded. -But- if your tce directory is on the ntfs filesystem, the loop mounted extension itself keeps you from unmounting/remounting that partition so it stays read-only. However, if you use ntfs3g.gz (a secondary initrd) or remaster ntfs3g into core.gz, then ntfs3g will be present before the partition containing the tce directory is mounted.
I think you could achieve a similar result by loading all of your "onboot" extensions, including ntfs3g.tcz, "toram" (copy2fs). That would allow you to remount the filesystem with the tce directory after ntfs3g.tcz is loaded, but it seems to me that loading ntfs3g in the initrd is cleaner.
There might also be a way to get the desired results using httplist or tftplist, but I don't remember the details of how that stuff works.