Current Guts and post Jinchuu Kenshin for reference. They swap places, bodies, and power/ability sets such that they're basically just trading personas and histories. Guts gets plunked down at the start of the Kenshin comic, and Kenshin gets swapped in post Eclipse after having been forced to read the entire Berserk series up to that point. How do they handle each others' lives?
Scenario 2: They fully trade places, keeping everything, except Guts gets his speed bumped up to... lets say Aoshi's level.
Scenario 3: After either of the above, they sit and talk.