This is definitely on my radar.
Providing a means of customizing the data columns and format for survey data is an obvious one, and I've gotten other requests for this. This isn't trivial to add, but not a huge deal either. I had originally envisioned this as a command on the <survey> element, but putting it on the <surveypage> would allow you the flexibilty to specify the data for each page, which is nice. Likely, I'd put it on both. You would use the <survey> setting as a quick way to set the default for all pages, and if you wanted to override that default, you could do so on a given <surveypage>.
I've also been toying around with ways to easily record a single line of summary data (for example the D scores in the IAT) in addition to the raw reaction time data. My first thought is to create a new element called, for example, <summarydata> that looked similar to <data> but could appear multiple times in the script if multiple summaries were desired.
Regarding the other post - I'll post my reply there. My apologies for not responding sooner, I somehow missed your question on that one.