Which ironclad layout best suits a convoy escort rebuild?

Which type of ironclad would make the most practical convoy escort against First World War surface raiders?

An ironclad frigate is the preferred starting point in this comparison because of its seakeeping. A barbette ship could also be useful against lightly armed merchant raiders.

An escort must be able to stay with its convoy in open water. Ironclad frigates are preferred here for their seakeeping, while barbette ships receive a separate, more qualified endorsement. The likely opponents are converted merchant raiders with relatively light guns and little protection. An exchange between ocean liners armed with 4.7-inch and 4.1-inch guns illustrates why the escort would not need battleship-scale armament.