Oh it is definitely not only theoretically possible for someone else to teleport a pure-born Garlean, technically we've already seen this happen at least once. It was presumably how Livia and her unit of shock troops were able to enter the Waking Sands and raid the place without being seen by the Immortal Flames guards patrolling Vesper Bay outside. Lahabrea teleported them directly inside - in his Thancred-suit he would not have raised suspicion and probably just waltzed right in through the front door past Tataru, and once inside thus could freely teleport Livia and her martial thugs inside before anyone knew what was happening.

Presumably the previously mentioned Garlean magitek transporter rings probably work in a similar manner to the spell by breaking down the body's aether and sending over wires to the destination gate.

But this is all speculation so take from that what you will.