Add Excel as a supported data source type
Backward as it seems, it would support platform-independence.
I'm developing an app right now for the small business where I work that interfaces with a SQL Server ERP to do unsupported processing before reporting. But, using Excel as a buffer means that if they change to an Oracle ERP I won't have to change the code - just create a query in the new ERP to generate the spreadsheet. Moreover, Excel is supported and working fine in the designer - it shouldn't take much to add it for the engine.