It would be great if you could allow customers to create a quote request from products listed as well as the shop owner being able to add a new quote via the back end in order to send to a client who can accept the quote and be forwarded direct to checkout.
It would definitely save the shop owner a great deal of time having it all in one.
Sagar Sheral commented
WisdmLabs has recently developed a plugin called QuoteUp which enables customers to add multiple products in an enquiry cart and submit the quote for approval. The admin can approve/reject the quote or negotiate. It also allows the admin to hide the add to cart button and selectively enabe or disable QuoteUp for a specific product. Here's the link:
Hope this helps :)