Joint management and exploitation of the area does not necessarily preclude the free flow of civilian traffic in the area. In fact that is the last thing anyone of the claimants in the area would want to happen considering how much these nations depend on maritime trade.In the eyes of the world especially nations that depends free passage of the area, that is a very poor and selfish excuse to ENCROACH international waters claiming as their own placing missiles that is regarded as potential hostile provocations against any nation that are against PRC's claims.
And as for placing weapons, lets not forget that it was Vietnam and Taiwan that got the ball rolling first by placing their own first.
But nevertheless this is my opinion on the matter. And I still stick to it as the most optimal solution out of this mess of a issue.