Suggestion

I would like to suggest you to add a filter in flamingo_htmlize(), that will help people to customize it little better.
May not be where I have specified may be more flexible able to replace the list with something else. that will be great addition.

Please let me know, if it is possible or will some issue.

function flamingo_htmlize( $val ) {
	if ( is_array( $val ) ) {
		$result = '';

		foreach ( $val as $v ) {
			$v = flamingo_htmlize( $v );
			$v = apply_filters('flamingo_htmlize', $v);
			$result .= '<li>' . $v . '</li>';
			
		}

		return '<ul>' . $result . '</ul>';
	}

	return wpautop( esc_html( (string) $val ) );
}