It doesn't seem very compatible to the whole series to me. Firstly, it seems to show that all characters were NF-related, as opposed to half of them being Morcians in the series. Secondly, you might have noticed that in ToF Sir Shadow seemed to be aging backwards. When we were writing it, I intended that eventually he ends up young, to the surprise of everyone who until then had always knew him as really really old. This is a quite different interpretation of Wiz's dual appearance. Thirdly, it certainly couldn't be before the Syntax War (not unchanged, I mean), because before going to Morcia the only Knights were the founders, Seton and Legoboy, while in ToF there's a whole bunch of people. Fourthly, Shadow's mysterious enemy is the same character in both stories and I would like his first meeting with the KotOS to be in a different occasion. Fifthly, Shadow does not appear by the end of Scattered Ashes (lots of them concern Wiz, but that's because I know him best and I know my intentiond for future stories concerning him).
There might be others I do not recall. But I think it was a general thing.
My opinion is that the last idea is the best.