The ShB equivalent was definitely the world visit sytem.

Flying and Swimming were both modes of transport, referenced canonically in game.
World Visit might have come (barely) before the actual launch of ShB, likely for technical reasons, but the link to travelling between the Source and the First is undeniable.

As for what could be added for 6.0?
Honestly I think they're running thin on ideas like this, I feel like they planned for these three things and they're spent.
They may try to come up with something new, but it won't have the same impact.

I suppose if 6.0 has a time travel plot again they could reference the completion and streamlining of NG+.
Or maybe a new form of instanced housing could be referenced, but that's a long shot.