Yes, yes and yes! Why limit topics to stuff where there's no objective answer? There are a lot of people (including people with 20K rep+ on SO) who quit SO in disgust and who would just love to share their knowledge on both objective and non-objective question. Pivot immediately. Do both objective and non-objective : ) Instant winner IMHO, going to help people there immediately!
Solving the objective question problem is and always has been SO's mission. It's a hard problem, and they solved it well- at least partially by firmly avoiding discussion questions.
So, while I think there's totally room and a need for a better solution to discussion questions (and there are several active attempts: discourse, slate, quora, etc), I hardly see it as a fault of SO's that they pushed away subjective questions.