/**
 * Allow anyone who can edit a page to revisionize a published page.
 * They won't be able to publish the page but they will be able to submit their revision for review.
 *
 * @param  boolean $is_enabled Default permissions value
 * @param  object  $post       WP_Post object of the post in question
 * @return boolean             Can the user revisionize the post?
 */ 
function namespace_filter_revisionize_is_create_enabled( $is_enabled, $post ) {
    return ! \Revisionize\get_revision_of( $post ) && 'page' == get_post_type( $post ) && current_user_can( 'edit_pages' ) ? true : $is_enabled;
}

add_filter( 'revisionize_is_create_enabled', 'namespace_filter_revisionize_is_create_enabled', 10, 2 );