I got this idea for a site I've been on that recently closed. Essentially a mission can be anything and would follow this format Name: (Name of the Mission)
Location: (Location of the Mission)
Skill Level / Difficulty: (Difficulty ranging from Novice, Beginner, Moderate, Expert, Master, Suicide)
Description: (The description of the Mission)
Success Conditions: (The conditions needing to be met in order to succeed in the mission {IE: protect a senator} )
Members: (How many members that can join, from 1 to as many as needed)
Reward: (The payout of the mission, ships, credits ect. ranging from Novice - Low, Beginner - Below Average, Moderate - Average, Expert - Above Average, Master - Doubled Reward, Suicide - Quadrupled Reward)
Each mission would include someone watching over the mission. A moderator for that mission that would answer Did Is from the players, or throw in curves for the simmers to deal with. Their reward and success would be judged by the quality of their replies during the sim.
