Yes, I would also very much like frequent incremental updates.
However, even if this was supported in Calibre (which is not AFAIK) or if you implemented it, the major problem is the lack of support by Kindle. So even if Calibre downloaded incrementals only, it would still have to send the complete issues to Kindle, thus you would only save a bit of bandwidth.
Actually, even sending multiple complete issues in the same day is not handled properly by Kindle:
https://www.mobileread.com/forums/sho...09#post1217209
So to conclude, I am afraid that this is up to Amazon developers and the only way to do say hourly updates is to send the complete issues (eg using dwanthny's workaround, although adding hourly/other updates should be very simple to implement in Calibre) and then read them from the 'back issues' collection...