The "default" export is the export that is specific to the "Stats Genie" site. Actually, with the exception of the HTML and Print options, all tournament exports are partner specific. Unless you are referring to exporting from the Players tab, in which case you can already define the fields you wish to be exported.
For tournament exports, I usually provide a format specific to the consumer - which is the partner which will be consuming the exported data, like a stats website. I'm always open to other ideas, though.
The issues with providing a customizable export option for the tournament using existing formats (CSV or XML) are
(1) CSV is easily customizable, but each row typically describes an individual of a group of the same thing (like each row describes a particular player). If that's what you want, why not just use the export on the Players tab?
(2) XML is a great format for including everything you want, but making it customizable is NOT an easy thing. Implementing an interface for the user to create a customizable XML export is no trivial task.
If you want an export specifically for your joomla component, why don't we just work on that?