If I understand correctly, on History SE we want to have questions that are precisely answerable and don't ask for open-ended lists. That makes sense. In light of that, would questions like the following be acceptable? Would they lead to a slippery slope, and if so how would we assess which ones are okay?
Example 1: Is there a daily record or reconstruction of the number of court visits per day to any one of the queenkings of Widgettia for an entire single year between 1600 and 1610?
Example 2: Are there any examples of a reconstructed Widgettian blarg ship? If so, pick one and tell me how long it was.
For each of these questions, there could be a finite, manageable-ish but still possibly large number of distinct correct answers. There would be a rules-based way to decide whether an answer is correct but it might stray too far into list territory.