1.one为a more capable leader的同位语,而with strong will and as well as good humour为介宾短语做后置定语修饰one.
即：一个有着强烈意志和良好幽默感的领导者.
2.如果用who引导定语从句,则该定语从句没有谓语动词啊.
with strong will and as well as good humour是一个介宾短语,它不能做从句的谓语.
3.如果用who,必须改成：who has strong will and as well as good humour.