Backend:

Configuration settings including only one field to enable/disable extension.

Frontend:

a.When customer add products into the cart, it will be showing like this:

Note: The item selected check box is for end user/customer to select and unselect product from the cart 

b. Customer can select/ unselect the product items, as per their requirement:

See below example :

Customers can unselect the product from the cart and they can proceed to checkout. 

Kindly note:

A.  Product price/cart total price of the selected products will be updated after the proceed to checkout. 

B. Registered users can place the order with selected items and those remaining unselected products will not be stored in the customer cart.

C. Currently guest users can place the order with selected items, and remaining unselected products will not be stored in the cart.

1st image:

Note: when customer unselect the product & do proceed to checkout with selected items then selected product will be showing with updated price on the checkout page i.e. strive shoulder pack (See image 2nd)

2nd image