Use AI for learning for manual correction and links
In a lot of cases the indexing is terribly wrong because of the missing knowledge of the local languages and not understanding the manual writings, additional notes, comments, since it would require the language knowledge. The local language would help to distinguish between correct and mistyped family or first names. You also have to know the culture of time, how the writing standards changed. An indexer should also know the local Latin dialect, not just the native languages.
However, if you could teach an AI system to use the manual correct links into the manually corrected and maintained records, then you could automate a lot of correcting tasks for the indexes.