Our session has discussed changing from grape juice to wine at the Lord's Table, but decided against it. It was a lengthy and impassioned debate, but without going into the particulars, here's Matthew Henry on the subject, taken from his comments on 1Corinthians 11:
As to the visible signs; these are bread and the cup, the former of which is called bread many times over in this passage, even after what the papists call consecration. What is eaten is called bread, though it be at the same time said to be the body of the Lord, a plain argument that the apostle knew nothing of their monstrous and absurd doctrine of transubstantiation. The latter is as plainly a part of this institution as words can make it. St. Matthew tells us, our Lord bade them all drink of it (Mt 26:27), as if he would, by this expression, lay in a caveat against the papists' depriving the laity of the cup. Bread and the cup are both made use of, because it is a holy feast. Nor is it here, or any where, made necessary, that any particular liquor should be in the cup. In one evangelist, indeed, it is plain that wine was the liquor used by our Saviour, though it was, perhaps, mingled with water, according to the Jewish custom; vide Lightfoot on Matthew 26. But this by no means renders it unlawful to have a sacrament where persons cannot come at wine. In every place of scripture in which we have an account of this part of the institution it is always expressed by a figure. The cup is put for what was in it, without once specifying what the liquor was, in the words of the institution.