You can't load or save, and the 20min timeout is there to prevent too many actions from queuing up in the local cache before it sends it off to the server for processing for the region play. It seems the game saves via an action log (basically a "diff" of the city, to reduce network traffic), while the game loads the whole city state from the server. Quite different processes for complete offline support - you'd need to figure out a way to translate the actions into the complete city and get the game to load from that.
(Edit: clarify, if you were offline the whole time, it can't save and reload your city, have to be online to do so)
Not saying it's impossible, just, not as easy as they think it is.
The reason for it being some sort of action log is to allow the server to validate the data for the region play to prevent cheating for regular mode for the challenges.
(Edit: this is probably why the servers were bogged. It's not just storing and sending the city's exports and imports for region play. But it seems too many cities and having to process and validate the actions in the database. This is why cheetah speed was removed temporarily, less speed, less updates for the server to process.)
Oh, and still no region play, which, like it or not, is still part of the game's overall design.
Not saying it's the best way to go, would be nice to allow sandbox mode to be offline though, since it'll ignore any validation anyway.
Also on the city boundaries, remember not everyone is a hardcore gamer that has a computer that can play a top of the line UE3 game or Crysis 3 at max quality. I know a number of Sim fans who don't have top of the line computers, so it's to provide a common baseline for the region challenges. Then add in all the agents and pathfinding and rendering and yadda yadda.
Wouldn't be fair to have say, a leaderboard challenge for reaching 2.5m population, then allow someone with an i7 + GTX 580 Ti + 16GB RAM to play in a 8km^2 city and just zone residential across the whole place, while someone on a laptop might have struggle on the 2km^2 plot.
Not the best way of going about it, mind you, but I understand why it was done for balance purposes.
I would have perhaps done it along the lines of classifying the regions based on TOTAL playable area size, and then offered various sized city plots configurations to fill that amount. Then limit the challenges to those classes (it is a challenge after all).
Reach 2.5m population on Class 'A' regions, total area size of say, 4km^2:
- 4 x 2x2 cities
- 1 x 4x4 city
- 1 x 2x2, 2 x 2x3 cities.
- etc.
But then you could run into gameplay balances, like do you still limit the 4x4 area with 3 streetcar terminals, or allow them to go up to the proportional 12? Maybe 6, like +1 terminal for each equivalent standard size addition? But ... would it be fair? And how would a sim path find across the big map? What would the CPU load be like with 10,000 of them trying to do so? We know the AI is pretty stupid, but how does it scale up?
Obviously, not everyone's interested in the region play and challenges, and some/a lot resent being forced into it. Maxis really should have pushed this as like SimCity Online just to temper expectations, instead of regular SimCity.
