I have a dataset which has a country field in it (about 50 countries). I basically filter my dataset (about 1m rows) per country and then create an IOK file for each country based upon a template. I use the batch block output in DataManager out had an idea for a new output block. It would basically combine a record filter and an output block. You would select one column to split the data by and it would create an one output file for as many items in that category that was split and create a file name based upon a mask (similar to the timestamp mask) and then append the split name to the end of the mask.
eg - Split by: [Source Country] File mask: Country Detail File - Template: Country Detail File Template.iok Output Type: IOK/IOM
This would have less functionality than the batch output but would enable much quicker splitting of data files into multiple files.
If you think its a good idea, would be happy to discuss further