Nowadays if a developer/partner has multiple apps that extends the same table, a sql table is created with the base table name adding a suffix with the id of the extension.
If you create a page with only some fields of base table, the sql query poulates all fields of base table + extensions, using JOINs for each extension, and that reduces perfomance. SetLoadFields in pages not allow to reduce the number of fields of the sql query.

I suggest to add a new param in app.json, that allow to change the suffix id of the table extension by a new GUID. If this new param has a value replaces de id of the extension in the sql table name suffix.

With this change, a parther or developer with many extensions, can setup all our extensions (or group of extension) with the same id, and that will group some table extensions in one sql table.

This can increase the perfomance of querys when a query need to access to all table extensions, since there are fewer tables and therefore fewer joins.

Best regards,

José Antonio López