A shop admin might not be open to give replacement option for all the products. In this case there should not be an option for replacement in customer side (My Account page -> Orders -> Request Warranty). This issue can be solved by giving an option to override default for 'return request types' for each order. Default option screenshot below.

A shop admin might not be open to give replacement option for all the products. In this case there should not be an option for replacement in customer side (My Account page -> Orders -> Request Warranty). This issue can be solved by giving an option to override default for 'return request types' for each order. Default option screenshot below.
