Not sure if OVF has the capability to configure the image on the fly, which is really whats required to deploy templates... At the very least you need to set IP, hostname and user/root passwords.
Perhaps define a template format which includes filesystem images, a script and a manifest... You create the disk image, populate it with a partition table (using user specified sizes for all the mountpoints defined in the manifest, plus swap), run resize2fs or appropriate command to expand the templates to fill the created partitions, you then run the script telling it where the filesystems are and it creates a proper fstab, sets user passwords and configures the network.