Marketpress request

Is there anyway that the marketpress template-functions.php editable? I think the only real long term complaint I have about this plugin is it's in ability to modify key aspects of the checkout page and the products list view. Clients always want the ability to add extra columns with extra checkout calculations or rearrange the products title > image > excerpt > price > add to cart to image > title> excerpt>... and so on. And basically, every update, I have to go through and modify it all over again. I hate modifying but I can't fight the client.