I think the Spark is still something higher than "being extremely smart and creative". Glassvitch and Merlot were not able to complete the Baron's device despite his instructions - this is partially because the device was designed to be faulty, but even before that Merlot wasn't surprised they were unable to complete it. The Spark involves actually warping physics to create devices that cannot be recreated by anyone but another Spark, which is why Merlot is so frustrated that not having the Spark puts a limit on his achievements that even an uneducated farmboy might surpass. A lower level Spark may be able to re-create the works of a higher level one, especially if given instructions (see: Dumedd transferring Ottila into the giant cat clank). But the Spark is still necessary to do so at all, even if the most competent non-Spark were to take the device apart with instructions and try to put it back together again.

I'm convinced that the final conflict in the story will be the decision over whether to get rid of the Spark or not. The first time window is just too clear - the Muse of Time/Lucrezia/whoever is addressing Agatha and asking if she really wants to return to how she was at the start of the story. The answer to that question should be interesting.