While looking at the new Confidence display, the “Negative Assertion” expansion in the GEDCOM7 specification came to mind.
Will Gramps 5.2 be able to support this? It seems like the data is simple enough that it could be a simple custom type for Attribute or Role. But the interface showing exclusionary data and logic building timeline seems complex.
I think properly handling this will require some thought, as well as potential core data model changes. Once done, all reports will need to be examined to see if/how to update to display the data.
I would expect GEDCOM 7 support to be a fairly large effort, potentially needing a Gramps 6.x release.