Fixing theme: Debating best way to change a function.

I’m currently using a theme that someone created with no intention of making it for general use, and fixing it so that it can be more adaptable. I’m doing this by creating a child theme.

Currently, they have no navigation menus that can be changed within wordpress. They have a header and a footer menu that they are calling in their functions.php through an array.

$common = array(
	'header' => 'https://common.radio.org/header/responsive/header.html',
	'footer' => 'https://common.radio.org/footer/responsive/footer.html',
);

function load_remote_template( $component = false, $query=false ) {

	if(!$component) {
		return false;
	}

	global $common;

	$url = $common[$component];
	$key = md5($url);

I’m trying to decide the best way to change this but keep the same design. I considered removing this function entirely in my child theme and create it from scratch using the same CSS settings, but I’m getting an error when I redeclare the function. I also considered creating a new HTML file and just changing the array values.

Anyone have advice on the best way to go about this?