Many good ideas here, but I only have one request:
No grinding please.
My thought would things would be working regardless of online or offline, so if you have flight downtime, whatever you had working in the background as buisy-work could be either be done with you on or off. There would be incentives for efficiency if you were on though. My reasoning behind such a suggestion is to cater towards casual play that doesn't require a bottomless pit of time (or grind) to do something. With the pressure to be online always doing something gone, things would be a lot more reasonable. Sure, these mini-games are meant to fill dead time in a design, but they also shouldn't require you to have to endure that time if you don't want to.
An example of a setup like that would be the queue system for skills in Eve Online. You queue up a lot of actions to be done and they do thier things. Some interaction is required but it's not going to consume every waking moment to keep things progressing. The idea is to make flight time meaningful, and not make it a grind in the process. The trick is designing the balance.
I have no issue with the idea of coordinating MMO add-on if you guys are ok with it. I was a project coordinator for several years over at WorldForge.org, so that's no real issue. The key should be getting a solid design down on paper and keep refining it until there is consensus, lock the feature set and shoot for our first milestone build.
As for those not wanting to do it. I'm not so sure that is the issue. It's more a matter of getting the resources together with the ability to communicate with everyone in real-time and via forum. I'd suggest for a project of this scale at the very least we'd need an irc channel, website and a sub-forum someplace to coordinate communications. It's not like something of this size just instantly has the people resources to pull it off. It means we'd need to recruit help over time and not expect instant results in the process. To do something like this is going to require at least a year of time to get right for v1.0. Heck, we could have an initial milestone out relatively fast, but that's just the first battle of many to see something like this in the form of where it needs to be as far as release quality and feature set.
The largest problem that needs to be addressed is just how all of this stuff can be done in a clean and well integrated manner within the Orbiter framework? This could be seen as using the Orbiter core but doing a TC for Orbiter that is so tightly integrated that it would need it's own install. I don't see how this could be merely done as somthing to slap on top of any old random Orbiter install. That would lead to countless quality control and consistancy issues. What I pose is that this "Orbiter Online" would use an Orbiter clean base isntall, then have the Total Conversion content installed over it in an all-inclusive manner as to bundle everything that has been through quality control asset review for this setup. That might go against many people's intent for this MMO concept, but if there is to be any consistancy to this, this would be an option to address it.