I don’t think this is possible.
Assuming that you are overwriting an SD card that has ltib generated image and rootfs, you may be able to replace the contents of the rootfs by simply copying over using a network.
You can also run an image from NFS as described in “i.MX SART Linux User’s Guide”. But again, you need a working U-boot on the SD card to do the NFS boot.
To make a SD card that is partitioned as it should and has U-boot (or preferred other boot-loader) you will need a card reader.