You could create a sales channel but it would be a lot simpler as you just need to push your products and inventory up to Kogan and pull orders back into Shopify. We have set this up before for other users on different platforms.
Bundleup - bundle your products and unbundle your orders. Channelup is a product data management solution helping Shopify stores automate their processes. If you require custom development or would like to test out our features contact me at email@example.com