The idea is to allow many people join a course and for everyone to start at the same time as a race, similar to "/pa challenge".

When a player joins a timed Challenge, a timer is initiated to allow for all the players that want to join in, once the time threshold is met (for example 10 seconds)
Then the course join countdown will start down and the join course functionality will start.

Not quite sure of the specifics yet, but it sounds fun.

Challenge signs will act like a usual Challenge. However a Player may be allocated as the host of the Challenge if a Challenge for that Course doesn't already exist. Any subsequent Players that join the Challenge using the Sign will be added as participants to the existing Challenge. The host of the Challenge must then start the Challenge using "/pa challenge start".