You can make the shipping required for orders with price add-ons by adding code to your theme.
This will combine the Shopify and Virtual Options on the invoice and orders.
Add this code to the theme.liquid file after our apps code. Here is more info on editing theme code.
<script>if (window.bcpo_settings) bcpo_settings.requires_shipping = true;</script>
Do not use this code if you are using custom shipping rates based on order price. This will cause and error not allowing the user to select a shipping rate and they are unable to checkout.