Multiple runways

I have seen several posts bemoaning the fact that the use of multiple runways at an airport is not permitted. I have seen aircraft landing and taking off on different parallel runways when neither closed for landing or take off. It seems that there are some issues however when the wind changes and crosswind issues arise for those runways not parallel:(
Perhaps full functionality should be incorporated when the most suitable runway and effective loading could be used in determining where a flight lands or takes off.

Well, I know what I mean:D