Untested proof of concept for a refactored Nexus WooCommerce Bridge plugin main file.

nxs-woobridge.php

<?php
/*
Plugin Name: Nexus WooCommerce bridge
Version: 1.1.0
Plugin URI: http://nexusthemes.com
Description: Add widgets/plugins and other functionality from WooCommerce into Nexus Framework
Author: Gert-Jan Bark, Jeff Brand
Author URI: http://nexusthemes.com
*/

NXS_WooCommerce::setup();

class NXS_WooCommerce {
	static function setup() {
		add_action( 'init', array( __CLASS__, 'init' ) );
		add_action( 'admin_notices', array( __CLASS__, 'framework_missing_notice' ) );
		add_action( 'wp_enqueue_scripts', array( __CLASS__, 'enqueue_styles' ) );

		// Nexus hooks
		add_filter( 'nxs_links_getposttypes', array( __CLASS__, 'nxs_links_getposttypes' ) );
		add_action( 'nxs_getwidgets', array( __CLASS__, 'getwidgets' ), 10, 2);

		// WooCommerce hooks
		add_action( 'woocommerce_before_template_part', array( __CLASS__, 'before_template' ) ); //"nxs_woobridge_beforetemplate");
		add_action( 'woocommerce_after_template_part',  array( __CLASS__, 'after_template' ) ); //nxs_woobridge_aftertemplate");
		add_filter( 'add_to_cart_fragments', array( __CLASS__, 'add_to_cart_fragments' ), 99 );

	}

	static function is_framework_active() {
		return defined( 'NXS_FRAMEWORKLOADED' );
	}

	static function is_wc_active() {
		return function_exists( 'WC' ) || isset( $GLOBALS['woocommerce'] );
	}

	static function init() {
		if ( ! self::is_framework_active() ) {
			return;
		}

		// WOO widgets
		nxs_lazyload_plugin_widget(__FILE__, "wooproductdetail");
		nxs_lazyload_plugin_widget(__FILE__, "woomessages");
		nxs_lazyload_plugin_widget(__FILE__, "woocheckout");
		nxs_lazyload_plugin_widget(__FILE__, "woothankyou");
		nxs_lazyload_plugin_widget(__FILE__, "woocart");
		nxs_lazyload_plugin_widget(__FILE__, "wooprodlist");
		nxs_lazyload_plugin_widget(__FILE__, "wooaddtocart");
		nxs_lazyload_plugin_widget(__FILE__, "woogotocart");
		nxs_lazyload_plugin_widget(__FILE__, "wooproductreference");
		nxs_lazyload_plugin_widget(__FILE__, "woominicart");
		
		// WOO business rules
		nxs_lazyload_plugin_widget(__FILE__, "woobusrulearchiveprodcatdyncontent");
		nxs_lazyload_plugin_widget(__FILE__, "woobusrulewoopage");
		nxs_lazyload_plugin_widget(__FILE__, "woobusruleproduct");
		nxs_lazyload_plugin_widget(__FILE__, "woobusrulecategory");
		nxs_lazyload_plugin_widget(__FILE__, "woobusrulearchiveprodcat");
	}
	
	static function framework_missing_notice() {
		if ( self::is_framework_active() ) {
			// @todo: i18n?
			echo '<div class="error"><p>The nxs_woobridge plugin is not initialized; NexusFramework dependency is missing (hint: activate a WordPress theme from NexusThemes.com first)</p></div>';
		}
	}

	static function enqueue_styles() {
		wp_enqueue_style('nxs-woobridge-style', plugins_url( 'css/nxswoobridge.css', __FILE__ ), array(), nxs_getthemeversion(), 'all' );
	}

	static function nxs_links_getposttypes( $result ) {
		$result[] = "product";
		return $result;
	}

	static function add_to_cart_fragments( $result ) {
		$result["div.widget_shopping_cart_content"] = self::decoratetemplate_minicart( $result['div.widget_shopping_cart_content'] );
		return $result;
	}

	static function before_template() {
		ob_start( array( __CLASS__, 'decoratetemplate_pagerendering' ) );
	}

	static function after_template() {
		ob_end_flush();
	}

	// Convert form into nexusform
	static function decoratetemplate_pagerendering( $buffer ) {
		$buffer = str_replace("<form ", "<form class='nxs-form' ", $buffer);	
		$buffer = str_replace("class=\"button\"", "class=\"button nxs-button nxs-button-scale-2-0 nxs-colorzen nxs-colorzen-c22\"", $buffer);
		$buffer = str_replace("button alt", "button alt nxs-button nxs-button-scale-2-0  nxs-colorzen nxs-colorzen-c22 ", $buffer);

		return $buffer;
	}

	static function decoratetemplate_minicart( $buffer ) {
		$buffer = str_replace( "button", "button nxs-button nxs-button-scale-1-0 nxs-colorzen nxs-colorzen-c22", $buffer );
		return $buffer;
	}

	static function getwidgets( $result, $widgetargs ) {

		if ( ! self::is_wc_active() ) {
			return $result;
		}
		
		switch ( $widgetargs['nxsposttype'] ) {
			case 'busrulesset':
				$result[] = array("widgetid" => "woobusrulearchiveprodcatdyncontent");
				$result[] = array("widgetid" => "woobusrulewoopage");
				$result[] = array("widgetid" => "woobusruleproduct");
				$result[] = array("widgetid" => "woobusrulecategory");
				$result[] = array("widgetid" => "woobusrulearchiveprodcat");
				break;

			case 'post':
			case 'footer':
			case 'header':
			case 'subheader':
			case 'subfooter':
			case 'pagelet':
			case 'sidebar':
				$result[] = array("widgetid" => "wooproductdetail");
				$result[] = array("widgetid" => "woomessages");
				$result[] = array("widgetid" => "wooprodlist");
				$result[] = array("widgetid" => "woocheckout");
				$result[] = array("widgetid" => "woothankyou");
				$result[] = array("widgetid" => "woocart");
				$result[] = array("widgetid" => "wooaddtocart");
				$result[] = array("widgetid" => "woogotocart");
				$result[] = array("widgetid" => "wooproductreference");
				$result[] = array("widgetid" => "woominicart");
				break;
		}
			
		return $result;
	}

}