This will probably come off as weird, but I actually have a direct answer for this one. I was one of a few people, I believe, that asked about cross server structures in an interview with Yoshi-P at the Stormblood pre-launch event last year! I want to say MTQ also asked something similar, though I'm not 100% sure.

Though it was for the general community at large, not specifically targeting the roleplay community. That being said, the answer I got from Yoshida was more along the lines of "We've been looking into the idea of making it possible to teleport to a singular zone on another server."

So, if you were on say Gilgamesh, you might be able to teleport to Balmung's New Gridania specifically. At least, that was the example I was given. He didn't say, however, whether or not that was currently possible or planning on being implemented. Just that it's something they'd been looking at.

No bamboozle.