Another thing you could try is to stream all the submissions from Aggregate to another server, and do the geo-to-KML conversion there. I did something along these lines to visualize geo-referenced XForm submissions directly in Google Earth, which obviously involved having to convert geopoints to KML coordinates, but you could just as easily extract and translate geotrace & geoshapes as well. See this thread for more details.
Failing all that, there's certainly no harm in floating the idea of a new geo-to-KML (or geo-to-JSON?) XPath function in Features [especially when you can offer some funding]. Certainly this long-lat format used (solely) by KML seems to be a well-known pain-point...