Have a notion of allowable number of sprint points, that is editable at any time (maybe we should store this per person but also store a history of change logs, so we know for which sprints they are allowed what numbers of points, should these things change?)
On the frontend -- in the people profile edits, have a max point allowed editor
On the sprint planning /reporting views for a project:
Display points a person is committed to not on just current project but across active sprints on all projects, in addition to claimed points on current project
Display points remaining across projects, in addition to points remaining here
On an individual dashboard page:
See all my projects and sprints associated with each project
See for the current sprint period, my burn down chart across projects
On the backend+frontend:
On the sprint planning /reporting views for a project:
On an individual dashboard page: