Changing login screen form elements

I'm working on a project where we are making a different login page for the users/clients. Based on the new template that we are trying to implement, I need to alter some of the buttons and input fields to use the new markup. I made a duplicate of the cms login form and am working off of that.

I need to take some of the button tags and turn them from <input> tags to <button> tags, and on the checkbox elements, make it to where I can inject a <span> tag inside of the <label>. I'm not sure how to approach this, as I don't want to change too much of the code behind because of functionality.

Any suggestions on how to approach this would be most helpful