I don't want to say they can't be mathematically modeled (in a purely theoretical sense they can), but it should be apparent by now that it's very hard to do well. I wrote a post on this particular issue a while back: https://steemit.com/writing/@blocktrades/alice-has-5-ice-cubes-bob-takes-3-how-many-ice-cubes-does-alice-have-left-for-her-afternoon-thai-iced-tea

On your second point, sure. Any change in rules can potentially cause the coin users to place more value in the coin, even removal of rules they don't like.