I would love to be able to give my clients access to the sales order form from the Sales module. I assumed it would be the purpose of the Portal but, apparently, it is read-only. 

My goal is to allow customers to create sales orders themselves, without having to go through the pain of browsing the catalog, adding products to the cart, etc. They know the reference ids of the products they're ordering so using the same form as the one used by my internal sales representatives would be perfect. 

Is there a module that might help me with that?

If I were to custom build it, would it have to be based on the e-commerce module?

Would I be able to repurpose/extend the sales.order.form?

Is the portal customizable?

Would anyone be interested in a commercial version of such a module?

Thanks in advance for any help.