Even with big hard drives I don't think the 400 billion star galaxy could be held on a local system. We would be playing a subset of the full game
That's fine by me. Honestly, it is. Having a galaxy with "just" 500 or so million stars would not limit my gameplay, nor would it make the game any less enjoyable. I must have played FE2 and FFE for literally
tens of thousands of hours over the years, probably more than any other game I've ever played, and I spent 99% of my time between the Federation Systems, the Imperial Systems and the Alliance, with the occasional stop at La Soeur du Dan Ham. I liked knowing that there were lots of systems around me, I liked knowing that I could have gone there had I chosen to do so, but I never actually felt the need to jump to some unexplored, uninhabited system in the -20,-57 sector, so in that sense, having 500 million or 400 billion systems makes absolutely no difference for me, and I know many other players feel the same.
The bulletin board missions would be limited in variety and would begin to get a bit same-y after a while.
Variety really isn't everything: have you ever played Skyrim? A significant number of the quests in that game is of the "kill bandit" or "fetch item X and bring it back to me" type, but there are so many of them, and the NPCs are so different, that they're always fresh and no two quests feel exactly the same. And anyway, once again, I'd be more than willing to play a "limited" version of the game, provided it was offline. I don't need anything particularly fancy: atmosphere and immersiveness are far more important for me than an ever-evolving world.
The economy could not be dynamically active, except in a very limited way and it might be necessary to have random elements generated within it to avoid it becoming entirely predictable.
Good! I don't want the economy to be dynamically active if by *dynamically* you mean "influenced by the actions of other users". I want it to be dynamic as the result of random in-game events and, most importantly, of my actions, nothing more, nothing less. And if I have to choose between static and community-influenced dynamic, I'll pick static any day of the week. Like I said, for me an immersive experience is better than a dynamic one, but there can be no immersion if my game is influenced by what other players do.
In other words, the game might become stale and predictable which is the last thing any of us would want.
A well designed game will not become "stale and predictable", not for many years, sometimes not ever. There are many cases of single player games (and not just sandbox ones) that became neither stale nor predictable, and they had no online mode, in fact, some even predate the internet. If ED has to resort to constant user input to keep things interesting, to me that is not a "feature", but rather a design flaw, unless the main goal all along was to have an MMO and the single player mode was just a bone they threw at the old dogs to lure them in in the early stage. Not to mention the fact that, as someone has already pointed out a few hundred posts ago, if the "dynamic" aspect of the game is so user dependent, what's going to happen once people start to lose interest and the active population decreases? Stagnation?
I hope I didn't sound rude or harsh: I appreciate the very reasonable tone of your post.