I posted a suggestion back in July that could help dealing with the Castle drop strategy. In this post of mine I suggested that a new unit called the [Staff Slinger] could be available when reaching the Feudal Age and trained from the [Siege Workshop], which can be built during the second age but it can’t train all of the other siege units from it until reaching the Castle Age and afterwards. The [Staff Slinger] will serve as a cheap but short ranged siege unit that will be effective against buildings in numbers.