The dimensional hub thing couldn't honestly have been done in a solo, because it was central to the team's future. The entire story was a setup for a new headquarters, one which the team can choose to accept or deny. It's not physically tied to the small Dawson Isle, though -- it's not physically tied to any one place, since it's accessible to the team from any doorway.
Just think about it:
The team can each live in their own homes, spread out amongst the island, but they can hold a meeting at the drop of a hat as long as they have the key with them. And they can return to wherever they were just as easily.
Are there limitations? Sure, we can think of some right away, if need be. It would be too easy to use the new HQ as a way to break into any place at any time, but for obvious reasons there should be some kind of limitation about that. Perhaps the HQ can only open a doorway in a "general area" -- say, Tucson, Arizona... but it can't open a doorway to a specific address.
