Web Developer with API Expertise

We are a 3PL company that warehouses inventory for retailers. When an order is placed online (Shopify, Amazon, etc) by a customer of the retailer, we receive the order, pick it from our warehouse, pack it, and ship it to the customer.

We have used various 3rd party software options like Shipstation, Ship Hero, etc, but we need something that fits our exact needs.

The solution we are looking for has the following flow:

1) The app (web based) should integrate easily with any retail platform (Shopify, Amazon, eBay, Woocommerce, etc)

2) An order is placed by a customer on one of the retail platforms

3) We receive the order in our order queue

4) The order information goes to a person with a device (like a smartphone) that can barcode scan the items in the order and prepare them for shipping.

4a) When the items are picked and scanned, the inventory is updated in real time across all of the customers retail platforms

5) When new inventory is received, it can be scanned in and the inventory levels tracked. The customer should have access to see the inventory that we are holding for them and run reports (sales velocity, best sellers, etc).

6) The system should be able to handle multiple customers and multiple sales platforms simultaneously and additionally be able to bill each customer separately based on the terms we have established with them

I have found an example of a similar software that was developed for this purpose. I can share a couple of screenshots if you are interested. The example was built with Admin LTE and bootstrap. This may be an option but is not required. We just want the software to function appropriately.