As someone already said (and you mentioned), they don't even have to do anything to the client too much really, but they could provide the server code and a means to run it on your computer and invite friends into your world or whatnot. Let it be tied to the system clock. If people want to cheat then, whatever, their world at that point. As I said, I'm really only hoping they'll consider/do this when they ultimately do take the servers down.

I think that's the best means as well. And if their programmers can't ultimately create a means for people to run their own servers and transfer their character data over to it, well, SE might want to find new programmers. It's work, no doubt, but it is their job.