Trader account with simple order form, pay by invoice and free delivery over £x

I have a customer that needs to set up an existing 2.1.0.1 OC account with a TRADE OPTION with some specific requirements that relates to both extensions and templates. I'm a frontend developer with good template knowledge but will need some support for both this and extensions that will allow us to fulfill all the acceptance criteria:

1. Trade customer needs to be able to request an account online to which an email will be sent to admin who will approve in the back office.
2. When the trade customer logs in to order products, they are presented with a very simple order form (see attached).
3. The simple order form will be a long table of contents split down by category. The categories are the same as the retail customers, bar a couple which traders won't have access to.
4. Each category is presented in a show/hide similar to the way the retail journey is when you go to each step. This will prevent the page from being extremely long.
5. When a customer adds the number of products they want, it updates the total cost for that product and a running total at the very bottom of the page. This will continue for each product under each category.
6. Under the running total at the bottom, we will have some conditional text that will display when the running total exceeds a certain amount.
7. When the trade customer is happy with their order, they submit the form, admin gets notification by email.
8. Admin will then process the order, and the payment and delivery are dealt with all offline away from OC.

I understand there's a lot of bespoke stuff here. Any help please would be greatly appreciated.

Cheers

If no extensions on the Marketplace do exist for such requests, create a new service request in the Commercial Support section of the forum (or this topic could be moved over there on request) to get these tasks done as a custom job.