Today all datatables will go into one table in PostGresSQL/SQLServer; as far as I know. This limits the capabilities for indexes or maybe even stored procedures to go beyond the ThingWorx data model. The current workaround is to create a new database and use SQL commands instead. (my knowledge).
It would be great if we can get z_* tables like in SAP for large datatables. This would allow using all predefined services without SQL but have the benefit, that every datatable has its own table representation in the database. Changing the datashape of this kind of table is a limit that has to be addressed in R&D. Maybe just prevent datashape change after used in an "external datatable"