Since Coinpayments can provide each merchant with the needed wallet and has the necessary API, I don't think we'll need Insight after all.
It will just be a matter of adapting Cryptowoo to use the Coinpayments API. For the initial merchant install, the exchange rate functionality can also be stripped since the item will be priced in GLD.
I've created a Wordpress site for testing the plugin:
http://www.coinbuilder.org