What I was saying is, the Crystal Tower will be huge and that we don't know if that attraction will still be in Mor Dhona in ARR. Chances are the Crystal Tower will emerge and the Agrias and Midgarsormr will be destroyed.

I was under the impression that we were trying to intercept the forces leaving Castrum Novum before they were able to get to Cartenau, where our GC leaders were holding the front lines. In the grand total of 10 minutes of that 2 hours the servers were up, I followed the action from the Castrum to the south and west, so I figured that's where they were headed.

Maybe there were some clues in the dialogue that mostly happened while we were offline, lol.

But, yes, you're right - the battle had to happen somewhere we could go.
Chances are if we had intercepted the Garleans directly north of Camp Bluefog, many lives would be lost in Ceruleum explosions..after all that's where the extractors are. So it only makes sense to protect something that has strategic value by setting the frontline even further north. Also the GC Leaders seemed to be taking the fight to the Garleans instead of waiting for them to come..and we don't know if anyone was in charge of the VIIth with Van Darnus having been disposed of.