As far as adding customers, creating orders, I don't see a need to do this with COWOA!
But I did find and tested something that would work for you.. In the plugin section you can find three plugins that do just what you need. I installed on a ZC1.5.4 and they did work, not the way I would like, but they do create customer, order and edit order which lets you add or remove products. Look for admin_new_customer then admin_new_orders and edit_orders-4.1.7..
Follow the instructions and suggested install order. The new order can be used to create a past COWOA customer order! With the edit order then allows you to add products. It works. I may change the code and create something that works for me.. If I only sold products, then this would be something else, but for me the store front still works better.
To add this function would make COWOA even larger and harder for folks to install and maintain/update is why I wouldn't suggest it become part of COWOA. Plus with the three mods supported and working why add another one.
With the changes I did to my site cowoa, master password does not work for COWOA accounts. When you change things so anyone with or without an account can do COWOA, I had to change how account access was performed or account holders would be auto logged in..