Write some Web Software / Website design

This needs to be a sophisticated website that automates a supply chain. The website will be designed to allow client user accounts and supplier user accounts. The purpose of the website is to allow client access in a simple platform where they can request services from a predetermined list. The service is emergency staffing and the sector is healthcare nursing homes and hospitals. The request for emergency staffing would be sent out to all registered supplier users. This request function would then trigger a submission of candidates from the supplier to the client. The client would see a list of submissions and their relevant information and cost etc. from this they would chose the preferred candidate and this would create an automated booking. the system would also have an e-signature process where the client can confirm after the assignment that the work has been done, thus creating an invoice for the services provided without the need for a paper timesheet. There is a lot of detail to go through to ensure the right system functionality is implemented but ultimately I need a system that can handle possibly 1000 active users at any given time + Please note, the system needs to be clean, tidy and basic in terms of use. obvious to navigate and easy to understand and use. No time wasters, no wordpress themes etc. this also needs to be built with the possibility of an app being developed to allow mobile access by the client, and also to allow the suppliers candidates to receive supplier requests from the system and to submit themselves to the vacancies if the supplier wished to utilise this later facility.