If I had to guess at the top 10 issues between the churches I'd say they are:
1. Primacy of the Pope
Yes, the role of the Pope of Rome would have to be evaluated. There is a good book by the Orthodox scholar Oliver Clement on the very issue. The understanding will have to be such that the Pope is not seen as \"over\" the other Patriarchs, while remaining \"first among equals.\" It would not only be the role of the Pope but the role of the whole Curia in relation to the Eastern Churches.
In Europe, the Eastern Catholics celebrate Pascha the same date as the Eastern Orthodox. But on a larger scale a common calendar would be helpful.
5. Jurisdiction (who is in charge of the Americas?)
If such a union were to occur, I do not think that the question would make much sense. The Orthodox Churches in a America would not see themselves under the Pope of Rome or any Latin bishop. The Eastern Catholic churches in America today already are under their own bishops, distinct from the Latin bishops. And for the Latins, I can say that they would never see themselves under a Metropolitan of All America and Canada.
IMHO, given the plurality of Churches in America, the best course of action might be to set up a conference of bishops (like the USSCB) but which would deal more specifically with relations between the churches.
6. Differences in iconography / or liturgy
I don't see this as a particular problem. The Eastern Churches would have to accept that Western statuary is not heretical. In terms of Liturgy, the Western Church already accepts the Divine Liturgy, and in the Eastern Orthodox Church, the Western Rite Orthodox Liturgy of St. Gregory closely approximates the Tridentine Latin Mass. There are other issues in present day Latin liturgy--e.g. serving facing the people, ad populum, having altar girls in the sanctuary, etc., and these would have to be addressed in some manner, but even within the Latin Church today there is disagreement concerning these.
7. Orthodoxy is more relational, RC is more legalistic so there is a mindset difference.
Yes, in emphasis I agree. IMHO, the West needs to rediscover the Patristic tradition, and the East needs to recognize that the West had its own particular traditions in the first millenium prior to separation.
8. Type / purpose of monastics
???
9. Type of bread in communion
The Latins and Armenians would use unleavened, the Byzantines and Copts leavened. When I went to a WRO liturgy, they used unleavened bread and gave communion by intinction (dipping the Bread into the Wine). There are other traditions related to the Eucharist that may be minor issue--e.g. \"first communion.\" In the Eastern tradition, baptized infants receive. In the Western tradition, only older children who have underwent \"first communion\" can receive. This difference exists amongst the Eastern Catholics and Latin Catholics today, but it's not a huge issue.
10. Cultural differences such as the RC's bless themselves to the right, Orthodox to the left.
Coptic Christians sign themselves left to right, like the Latins. It's not a huge issue, IMHO.
I don't know how much compromise there could be on some of them. Namely, the top 5 I don't see much compromise on either side.
Understanding of the Primacy of Rome would be big.
#7 is also big.
The addition of the filioque is a concern, as is the theology of it, although I'm thinking that from an Orthodox perspective, a specifically defined filioque of \"through\" the Son might make things clearer.
