The marketplace will be for specific clients and vendors. Each client and vendor will register and admin will accept the registration.
The admin will add all the categories and products. For each product the admin will add name, description , images etc and also assign that this product is available to X vendors.
The marketplace will show products (like eshop). Then the client will choose for example one product. Instead of add to cart it will have a button I want an offer. This button will actually send to all vendors that has this product an email. The email will let know that the client A is interested in product B.
Then all vendors will be able to reply back to client with an offer.
The client will check the offer and choose from which vendor he will buy the product.
Then an order will be created automatically and notify both vendor and client.
In all above steps the admin will be able to see everything. Every step, every notification, offer etc.
When order is created the admin will be able to update the order status. If it is possible also the vendor can update the order status?
Also it should follow the accessibility guidelines. It has to pass the IDI Web Accessibility Checker : Web Accessibility Checker ([login to view URL])
Also the admin wants to add products (like he is the vendor). Also he wants to add product in offer, with countdown (the offer ends in X days etc).