Goes from 1-2 concurrent players to some thousand, depending on
Well, yes, that's why I've created this post – probably, there are some known paths how to design this part of a game and not based on players counting.
It's not very interesting to run across empty terrain for half an hour, and not see another player.
Well, it depends on a gameplay, no? It could be crowded by players, but what if the game wants to make a feeling of unexplored territories? There should not be lot of players around in that case, only in some basic points (e.g., in cities). And at the same time, each player (or group of players) should be able to find "own piece" of that exploration (and still has a chance to meet other players, as in real world, not as in instanced games).
Just remove that large fallen tree which used to block the passage to the next valley
Probably, it will work for some cases, but hard to implement really open world with a path just blocked by some tree. It's good for a corridor-style games, where player have just a single way to go...
Also other issue with this way is that still need to develop those additional zones pretty fast (in case if game becomes successful) – or to have some buffer with zones which are unavailable to players – but it's taking us back to the question – how much zones need to have pre-developed?
While this make sense for alpha/beta tests, thank you!