It is possible to remove an existing deputee and replace them with someone else. There are many reasons why this may be appropriate but the main ones include a breakdown in the relationship between the existing deputy, the person they are representing or their close family circle, a breakdown between the different deputies if there are multiple deputies appointed, concerns about the suitability of the deputy to make the right decisions and finally the existing deputy stepping down because they are retiring / they are struggling with the responsibilities of being a deputy.