For example, the fiscal year overlaps check could be rewritten using an Exclude constraint with the range type .
The problem is that sqlite does not have the range type (nor the overlap operator). Indeed range type is specific to PostgreSQL.
But the overlap constraint is a common need for resource planning so I think we should have tools for that.
I think it must be possible to create an python-sql Operator to use in Exclude that will be converted into a composed where clause for backend that does not support range.