No, that wouldn't really work. Following that rule, a chaotic Spirit Magic user would be better off picking one type of dogma to use (say, detrimental) and making all of her choices of the other category deliberately bad. That way, she would be negatively affected by her spirit only half as often as if she had chosen dogmas that she had intended to use. Plus, without any limitation on which dogma she can use on any given turn, she becomes effectively twice as versatile as the good or evil spirit casters. This restriction gives her exactly half that versatility each turn, balancing it out perfectly. It also makes it so that if she does attempt to make one type of dogma dominant, she'll be hindered half the time, exactly as often as the spirit is.