The Holy Spirit isn’t a means. He is a Divine Person. Last I checked the Church was called the Body of Christ. I suspect that might have something to do with the Incarnation. The humanity of Christ is the bond between members of the Church by the working of the Spirit, which is why the Eucharist holds center stage. To take the Spirit as the unifying principle smacks of docetism and an impoverished view of the resurrected flesh.
2) Authority of Tradition
He can’t believe that the Scriptures are “unchangeable” with respect to the canon, for on his own principles the canon is a fallible set. What Scripture is, functionally for Protestants is a more or less fluid set of books. They modified the canon in the past and I see no in principle reason why they could not do so again.
And even if Scripture were the only normative source for teaching and practice there are I’d wager lots of practices or beliefs that have no explicit support in Scripture such as the perpetual virginity of Jesus or admitting women to the Eucharist.
And even if Scripture were the only infallible rule, the question is, who is the judge that is to normatively apply the rule?
3) Static cultural adaptation
I think we should preserve the Jewish forms of worship from the synagogue and the temple, albeit transformed by Christ. Jesus seemed to like them. To be Jewish in this respect is hardly “syncretistic.” And it is to be quite relevant for it keeps the church from having to follow after silly cultural trends and aestheticism and reinvent itself every five years like our existentially sick culture. It sends a message. We are not your culture. We are about something bigger than your culture. We are not a fad and we will outlast them all. People who constructed the great Cathedrals of Europe understood this. Moreover, they also understood the relevance of the Incarnation to architecture. With contemporary Protestant architecture, and no small amount of Puritan architecture as well, God is everywhere in general and no where in particular. So much for the Epistle to the Hebrews.
A big part of the divine liturgy is about meeting God in the life of Christ, which is why the Liturgy and the church year are centered around “doing over” the life of Christ. Historically it seems to have done a far better job at making people “holy” than the pop evangelical styles. Evangelicals have values but they lack virtue.