Well, if sim city or similar would be developed in a more open style, as first person games like quake etc tend to do, mods would be possible. I'm not saying you could just take pontifex as is and link with simcity as is. But maybe it would be worth approaching someone developing a game like that with the suggestion. It would open the game ot a much large audience too! There are people I know who find the idea of a bridge building game a little odd (####, I did till I tried it) but who will happily spend hours planning how to best place police stations.