The functionality described is much desired by organizations and does not exist today in WordPress.
I’m describing the ability for members to pledge or volunteer for a specific event. This functionality would really help political and other non-profit organizations. Characteristics of such a plug in would include:
1. Ability for users with the Contributor to create events. These events would then be subject to review by Editor and Admin. If approved, the event would appear in the calendar.
2. Events could specify the number of volunteers required.
3. Members could pledge/volunteer for specific events.
An example is a political rally. The event creator wants at least 20 people there. The event specifies 20 people. As members login and pledge to be there—the count is decremented and everyone can see which members pledged to be there.
This would be a fantastic plugin especially for political organizations. First, there are multiple organizations working together (County, Township, District, Candidate). Each has their own website. If I am running a County website, I can create accounts for each candidate (Contributor role) and these contributors could add their candidate events to my calendar.