So what happens when an f/o is made up to captain? He/she having no experience of taxi, RTO etc would have to spend a lot of extra time learning these new things. In my company both pilots perform all these tasks if it's that pilots sector. F/O is even encouraged to make "command type" decisions, under supervision of the captain of course. These means the transition of RHS to LHS is theoretically easier and improves confidence in the f/os handling and decision making abilities.