For anyone that is interested, I have converted the KOBO and KOBOTOUCH driver over to apsw. It turned out to be a lot quicker that I expected. Especially when I refactored all the database connects out to a simple method. I did some other refactoring for some code that was almost the same between the two drivers.
The code is in my branch at
https://github.com/davidfor/calibre.git. If there are any other Kobo users out there who want to run from source and check everything works, I would be very happy to hear the results. This is especially if you have a WiFi or the original Kobo. I don't have one of these to test with. I can do some testing of this using my Touch. I think they will be OK, but would like confirmation.
This will have no effect on extended driver, my Kobo Utilities or the Annotations plugin. I will be making changes to the latter two after these changes have been released to use apsw as well.
My plan is to use this for the next week and fix any problems I see. If everything goes OK, I will create a pull request next weekend.