So, this one only works in fictional universes that include powers, though it could be modified.
There's two versions, so version one: when the soulmates go near each other, they switch powers (permanently) and you can have stuff exploring them teaching each other their powers.
Version two: whenever they are near each other, they switch powers, but they regain theirs when far away from each other. So it's hard to fight unless they adapt when near each other, but it could also be very effective as they fully understand their partners power and how to utilise it.
(Both versions of this could be modified to just switch talents, so it could be real world stuff if you wanted, but this seems so much more interesting in my opinion, also I don't particularly like realistic fiction, so I am thoroughly biased, and I won't deny it)

~Sylva

(Also, I mentioned a while ago about making an au oneshot book out of this. If I did, would you want original characters, or fictional characters, if the latter, any suggestions as to whk and which au?)