Kudos for trying to find a sensible solution, but most of these disputes aren't about determining which geographical area a person and/or their ancestors stem from - that would be relatively simple to resolve with sources which are typically available.

Modern nationality is a highly complex topic related to not only geography, but also politics, language, religion etc. Often a dispute is not about providing information on a historical figure, but about "claiming" important people for your nation so that your collective "historical importance" is increased.