Create a Custom Field buoy in SearchWP to have posts with that Custom Field be given arbitrary priority (i.e. explicit higher weight) than SearchWP's calculated result weight

gistfile1.php

<?php

function my_searchwp_query_main_join( $sql, $engine ) {
	global $wpdb;

	$my_meta_key = 'my_search_priority';  // the meta_key you want to order by

	$sql = $sql . " LEFT JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID = {$wpdb->postmeta}.post_id AND {$wpdb->postmeta}.meta_key = '{$my_meta_key}'";

	return $sql;
}

add_filter( 'searchwp_query_main_join', 'my_searchwp_query_main_join', 10, 2 );


function my_searchwp_query_orderby( $orderby, $engine ) {
	global $wpdb;

	$my_order = "DESC"; // use DESC or ASC

	$original_orderby = str_replace( 'ORDER BY', '', $orderby );

	if ( "DESC" === $my_order ) {
		// Sort in descending order
		$new_orderby = "ORDER BY {$wpdb->postmeta}.meta_value+0 DESC, " . $original_orderby;
	} else {
		// Sort in ascending order; place empties last
		// @link http://stackoverflow.com/questions/2051602/mysql-orderby-a-number-nulls-last#8174026
		$new_orderby = "ORDER BY -{$wpdb->postmeta}.meta_value+0 DESC, " . $original_orderby;
	}

	return $new_orderby;
}

add_filter( 'searchwp_query_orderby', 'my_searchwp_query_orderby', 30, 2 );