We've talked about this a while ago, but there are two fundamental questions regarding Catholic/Protestant churches:
- Should they be brought into unity?
- What would it take to make this happen?
Each of these questions is critical. To the first, I say a resounding "yes!". Unity should be a goal that is sought. I realize that others, however, may not share such a goal.
Assuming for the moment that #1 is not the issue, how could #2 be accomplished? This would be an incredibly difficult challenge, one the has eluded Christians for centuries. Still, "nothing is impossible with God", so unity is not out of the question.
The theological issues would have to be ironed out that began since Martin Luther. However, I believe that over the years, progress at common understanding has actually been made between Catholics and Protestants, so it's not as if they would be starting from scratch. However, there would still be massive challenges in this regard.
Another issue that would have to be dealt with is structural/administration. Would they exist as different "rites" under the same umbrella?
Are there other big issues that would have to be rectified?