[With the reputation system,] how hard will it be to switch sides once we have started going in one direction?

So there's no real clear definitive answer on this, because it depends. If you're switching sides to a reputation that is at the direct opposite, if I'm going from the order to the other side, then when I'm ranking up reputation in one, that might be decreasing it in another. So obviously then switching sides is much harder. But if I'm going to a neutral faction where it didn't really decrease it as much, it might be less. So it really is a variable experience, and I think it's been designed that way. Some factions will hate each other more than others. Some will like each other more than others. So that's the clearest answer I can give, because obviously it's not just as simple as everybody hates each other or vice versa.