I know this would be a fairly major change since it would require changes to the admin systems but here's the suggestion:
Have GuildBank Uploader integrate with GRSS DKP sync (the download) and with GRSS upload and GroupCalendar upload.
The reason I think this will require a change is that we can't assume that either GRSS or GroupCalendar uploads should automatically be imported, so there would have to be a system where they can be uploaded to temporary storage on the site and then an admin can go in and review and process those stored files.
This would be hugely convenient especially because we tend to do DKP the next day at work (Hurray for "work"!) and sometimes forget to bring the GRSS data with to do so.