The Garleans actually have reverse engineered Allagan cloning tech, but the exact circumstances surrounding it are a bit of a spoiler.
I actually kept asking about whether or not Raubahn could get a Barrett-style prosthetic arm to replace the one he lost to Ilberd, and the devs ultimately said the Garleans have that kind of tech but don't share it with the world. So it's possible, but beyond Eorzean technical capabilities. (Maybe the Ironworks can use that as their next big project.)