If all bread for the eucharist must be leavened then don't make wafersYou can have leavened wafers. It also makes for easier shipping I'd imagine.
if unleavened bread is an acceptable Western practice, then don't leaven themI believe we use leavened because unleavened is not acceptable to the WR.
But the whole form of the wafer comes from the tradition of using unleavened bread. Essentially you are making leavened bread to look like unleavened bread. As I recall, the basic argument against unleavened bread made by the East is that the leaven represents the resurrection- the bread rises like Christ. If you're not allowing the bread to puff up the symbolism is defeated. If unleavened bread is not acceptable in WR, then this is a concession that the West was in error long before the schism. I thought the whole idea of WR was that the pre-schism West was equally Orthodox to the East.
Before the bread is pressed into the flattened disc, it does indeed rise like any other leavened bread would. But I also believe there is more than one way to make them, some perhaps not being "pressed" but being baked directly into the smaller wafer shape. But either way, the leaven is there and the bread does rise, if not as drastically as an entire loaf would.
As with many things in the Orthodox Western Rite, this is likely a theological change that simultaneously preserves the long-established tradition in question. In other words, what has become a normative aspect of the organic tradition in the West is preserved to whatever extent possible, in content and form, while only changing (and thus fulfilling) what needs to be changed in order to become fully consonant with Orthodoxy. This ensures the continued organic development of the tradition while also pointing it in the right direction; the faithful are not scandalized by the hijacking of their traditions, yet their heritage is now, in a sense, fuller
and more closely connected with Orthodoxy.
Other examples might include how the Rosary is prayed (eschewing "imagination" for an approach that uses Scripture, thus rooting it deeper in the ancient Western tradition of lectio divina
), kneeling on Sundays (less about penitence or more about awe and reverence; "Come, let us worship and bow down, Let us kneel before the LORD our Maker"), or even the mere adjusting of texts in the Mass to preserve the feeling and flow of the language, whilst totally shifting its meaning (for example, correcting "Who by His one
oblation" to "Who by His own
oblation" in the Mass of St. Tikhon).