A lot of this thread seems predicated on the idea that forcing people into the game world will make the game better for you.
What about the people that just want to tinker with the physics and engineering mechanics at their own pace? I see no reason not to let them. They're paying the entry fee all the same to have their own fun, not just to be your world decorations.
The idea is it would make the game better for everyone, and there's always the possibility to interact with someone, so they may get emotionally pulled into some cause when they didn't think they wanted to participate in the first place. The same systems can be developed for you to be able to tinker with the engineering and mechanics of the game at your own pace, but in doing so, your actions also act as world decorations making the game feel alive.
"I see no reason not to let them." One reason is because an MMO survives by having players around, and if the game defines itself as an MMO and then 50% of the players go into the offline mode, or worse, if 95% of the players form their own dead server, it devalues the promise of the MMO component. The entry fee paid is also voluntarily paid by the player, based on what the game offers. Not everyone can be made happy; some people will dislike the ships or the colors or drag in space or so many other things with the game. I default to the position which I think is most beneficial for the growth of the game. If the game is an MMO, and a player's intention is to sit offline and build a ship, the MMO component never has a chance to grow with that player's input.
We have evidence that this kind of system leads to immense meaningful gameplay; in EVE and SWG for example among others. If you wanted to play, you had to play the one and only game universe. You'd never have seen 1000's of people fighting in EVE, or hear of dramatic stories of loss and gain, if people could escape to their own universe. When you're forced to deal with the one universe, you have to make a choice - do you want this gameplay or not? If you want that gameplay, you can only get it in the one place it's offered on the one live universe. There gives the chance that a player will be drawn in to interacting with other players, and the game world stays alive and thriving. I liken it to a nuclear reaction, where a critical mass of players has to exist to generate enough activity to self-sustain. Many games cut short that possibility - either because their netcode doesn't allow that critical mass, or because the servers cannot handle the load, or because the players just never really got involved enough.
If you as a player want to engineer and tinker; doing so around everyone else even if you never talk to them provides value as people see some random robot working on a ship. You might not like being window dressing, but that's reality. If you go out in the world, people look at you. They might simply see what you're wearing and that could influence their entire day. WoW for example, people would see your shoulder-slot item and say "that's cool, I want that." If you could have obtained that gear offline, no one else gets inspired to try and get it too. This is very important that these little things be allowed to exist in the MMO space where the shape or style of your ship - which you are tinkering with without regard to anyone else - inspires the next best fighter design that shapes the future of the game world. You matter, even as a random tinkerer/builder, even if you never directly interact with someone. Good chance though, that since you're connected, online, you will interact with others, helping to hit that critical mass of activity.
Another feature of online-only is players can't game the system by testing all mechanics offline. If there is the ability to freely spawn ship parts offline, then there's no reason to mine for materials or use the market or any of that bulk content. You'd just do it all offline, interacting with no one, and you'd be able to test every system and every game mechanic heavily in this artificial world. This is fine for a server-based game like SE, since their networking tech cannot handle it, but if we make sure players in an MMO are all held to the same rules; that their testing and so on has to be done in the same universe as everyone else, we achieve a more fair gameplay system where no one can get ahead by bypassing the time it takes to acquire things and test things. The gameplay becomes much more organic as people are forced to do all their tinkering and testing in the one game universe, and the game world grows with every interaction.
I think it's very important for a game to define itself. Is this an MMO? If so it should aim to achieve that. It can always fall back onto individual servers if for some reason the main MMO component somehow didn't work. But if the MMO component wasn't given the best chance for success from the start, because most players fell away to offline servers, the game never had the chance to become great anyway. That's why many of us see the value in online only gameplay.
And again, I'd reiterate the idea that you will still be able to do all the testing and tinkering - just around others. That would be the best solution for giving the game the best chance to succeed at being an MMO.
