If we were going to do it for the best optimized situation when every adjacent site went live, it would be way too large to RF engineer, manage and implement. Just as you have pointed out. However, it could be simplified to this:
How about two settings...early deployment and final engineered setting? Set the initial early sites deployment with very little downtilt. When adjacent sites start to come online, use the internal downtilt adjustment to reset them to formal and final engineered settings. Since there is this trick remote controlled adjustment that can be done, it's a shame to not use it to your advantage now in early deployment.
Robert