I'd let someone put it in my place as long as I picked the spot and could make it look cool n shit.
An underwater hub would be cool, but I don't think that we don't have enough space to do it on the surface, I mean, our server is huge. I think a floating one would be pretty sweet, a collection of floating islands connected by bridges, each island for a different teleporter, possibly themed based on the place (sandstone for desert environment or just each person's building style).
Either that or like a huge open park enclosed by a tall but simple wall, with flowers and trees arranged in like a french style garden, with like, pavilions for each teleporter.