I'm hoping to make sandbox co-op campaign that plays like Darkstar One or Galaxy on Fire 2. I've never played Freelancer, but from what I've seen it looks to be about the same. I don't know much yet about what can be done or how to do it, but I just want to put up some ideas for feedback, as I need to know what kind of foreseeable problems there might be with my plans.
1. I want one mission to be the players base, where they can make purchases and allow other players to join as wingmen, with additional missions that represent different systems the player can visit freely. Is it possible to set up non-linear campaign missions?
2. I want the player to earn money and XP to use on purchases and upgrades. That by itself should be relatively simple, but I also want to be able to buy ships and weapons which will be stored in a hangar. I want to restrict available ships and weapons based on the player's XP level.
3. I want the player to be able to purchase upgrades for their base, which also cost money and are restricted by XP. For example, I want a higher level player to be able to purchase a shipyard and build capital ships that can be called in as reinforcements in other systems.
4. I want to emulate a persistent economy. I hope to use some variables and SEXP's to manage events across all of the different systems to make it apprear as though they are interacting in real-time. For instance, I want the player to be able to purchase trade convoys that will take goods and personnel to friendly space stations for trade. Would it be feasible to use SEXP's in one mission to manage what the state of another mission will be when the player loads it? I want to be able to send a convoy, watch it jump out, and follow it to its destination to watch it complete it's mission and return to the base. For another example, could the player be in one system when a random event plays and notifies them that their convoy in another sytem is under attack, and then jump to the system to fight off the attackers?