Build a Website - management website

I want a website that can help with management of a volunteer organisation. There will be several features to the website, with tasks to be allocated manually and automatically to various people (roles). There should be the ability for all members to log in to the website, with various levels of access to different functions. Features will include: - Register of members, with ability to allocate people to different lists (e.g. current members, former members, etc.), and different roles (e.g. maintenance manager, Treasurer, etc.) Register should be customisable, and different lists may require different information to be captured. - Mailing lists - Asset register - with ability to allocate assets to particular members, and have maintenance records and reminders for maintenance sent to maintenance manager - Attendance record - Calendar of events - Records section for storing/saving key documents - Ability to set tasks for particular members - Mobile compatibility - Online payment of fees - Basic inventory for canteen stock - NOT online sales of stock, but able to keep track of stock in/stock out and generate list to do stocktake against. This does not all need to be developed at once, but may be done in stages (e.g. payment capability is not needed straight away). In your proposal, please give me an indication of a proposed implementation plan, and detail any questions you have. This idea is still in development, so suggestions are very welcome. I would like to develop something that can, in the future, be replicated for other completely separate groups to use, so please keep that in mind.