Is it possible to move .custom-select styles to select.form-control? As it stands, it's only really useful if you don't plan on changing the border-radius on form-controls. By adding the form-control class to the select element we are already committing to Bootstrap's contract to style the element, doesn't make sense why we would only have partial control.

Edit: Also, .custom-select is the only custom element that doesn't need an extra element to achieve custom styles.