The warp lines would be nice to add, but the draw back:

1. There would have to be different warps, since there are so many camps and nodes. Making the spell/ability list longer than it needs to be.
2. It could only be used like FFXI as a return, but with return going to be set as 0 anima cost. What would be the point?
3. It would have to be set as, I am sorry I forgot how a rep worded it, an advanced role like Black Mage, otherwise everyone would have it. This still falls under number 2 really.