Gratia, Belhar is not yet incorporated because the requisite number of Presbyteries have not yet voted for it. To add something to the Book of Confessions requires the affirmative vote of 2/3 of all Presbyteries.
While one can learn from any of the confessions in the BoC, I agree with people who believe that our confessional standards have been weakened by so many different documents (particularly the Confession of 1967 and the Brief Statement of Faith.). It would have been better to just use Westminster and explain any scruples one has.
But I'm not in charge of such things ... just a humble country pastor here.