It will be simply HUB map (like in hexen), where main map is selection map (like stronghold one's)and every mission will be made by one <DM> member that will contain his challenges and (ofc) him.
The players will have to go through every challenge, as well buying some stuff that could help them.
On challenge map, firstly will the map maker introduce himself and describe what they will have to do.
When players will complete every challenge, they will go to the boss map, where they will have to kill every <DM> member (every one will have 1000 hp and special ability - like icedragon using Ice).