Would a Nicene Creed With Any Other Copyright Date Smell As Orthodox?

The "God-Fearin' Fiddler" has asked a series of provocative questions over at his blog, Army of Martyrs. The topic is the development of doctrine, and the Council of Nicaea's doctrine of the Trinity is being used as paradigmatic of the phenomenon as a whole.

The first point The Fiddler makes concerns the doctrine of the Trinity itself, and why we believe it. We do not believe it, he argues, because it is clearly taught in Scripture or because the post-apostolic fathers held to it uniformly (for it isn't, and they didn't). We believe it because the church lent to it her living and authoritative voice.

The Fiddler goes on to ask whether we would still believe in the Trinity if the Council of Nicaea had not been called until a few hundred years after it actually was convened. What about a thousand years later?

Building on point #2, the question arises: If the church can legitimately and authoritatively formulate the doctrine of the Trinity in 325, why can't it, with equal legitimacy and authority, formulate the doctrine of the Immaculate Conception in 1854? If there is an historical point after which all conciliar decrees become non-binding, when is it, and who determines it?

The Fiddler quotes N.T. Wright to the effect that if the doctrine of the Trinity hadn't developed organically, the church would have had to invent it in order to combat the Arian heresy. If that is the case, who's to say that the same rationale couldn't have been in play in order for the church to combat the errors of Protestantism at Trent?

Lastly, we are told that we do not have the right nor the luxury of picking and choosing with which ecumenical councils, and with which decrees of those councils, we choose to agree and submit ourselves. We either respect tradition or we do not, meaning that if some of the ecumenical councils are authoritative then they all are, and if one of them isn't, then none of them are.

Now the Reformed response to all this is to insist that we adhere and submit to the ecumenical councils insofar as their decrees are in accord with Scripture (the latter of which is ultimately authoritative, while the former are only penultimately so). But whose interpretation of Scripture? And if we believe them because they're biblical, then why not just read the Bible and save ourselves the hassle?

In short, must Nicaea bow down before me?