Forms, inputs and buttons are used throughout Moodle. Although they generally fall into a few standard patterns they are usually hand constructed each time without reference to a common design.

This makes them difficult to build, to use, to change and to upgrade.

A renderer dedicated to form items should be created. Starting with the most common patterns the individually created form elements should be changed to call these renderer functions.

NB: I've heard that in some sense the main forms in Moodle are incompatible with renderers. I don't know if that's true, or what the issue might be, but regardless there's alll sorts of hand-built forms already in renderers, and standardizing them would be reason enough to do this.