May be interesting to add different competition modes.

One of which could be a one time group competition.

For example, an office competition, a goal is set by the competition owner, they set the prize amount, % that goes to charity, % that goes to the winner.

They invite the participants and set the duration of the event.

Lots of companies have programs as part of their benefits to encourage exercise, etc. You could partner with benefits companies to set up the competitions for their clients.