I miss the agility to execute a SQL query of the "XPath query" directly on the database.
Especially when debugging or optimizing Xpaths.
Furthermore I experience OQL (or other modules) as time consuming and not fitting into the rapid development of Mendix.
Therefore I propose to show the SQL translation of the specified Xpath in modeler directly once entered in the Xpath field. Then you could directly execute the SQL query on the database to see the results/optimize Xpath.