499717 Magento seller feature

I need someone to create a multiple seller and location extension for Magento, where I can have multiple sellers of similar products in different locations. There will be a small amount of pre-defined locations. These will never change. At the front-end, users should to be able to search by seller or filter a category by seller. Each seller will need to be linked to a location (or several locations should they have more than one). It should also be possible to use location as a filter/search term. Each seller should have a trade login and will need the ability to upload their own products and special offers. Any uploaded products should be linked to the seller automatically. They should only be able to add products to categories that already exist. The creator of the product should have access to the special offer features in Magento, i.e. to list their new product as a special offer. Only the seller and the site admin should be able to edit products. It is acceptable to use the multiple store feature to create the locations as long as each requirement listed above is met. The finished product will be capable of filtering by (1) Category, (2) Location, and (3) Seller, in no particular order. There will be quite a lot of Magento work for the winner of this project.