It's not like there's any major problem with that, especially considering that I played a very similar character in Kingmaker (and I will probably play it again in WotR later down the line). I just wanted to point out that a build like that would have probably caused a mini-stroke in our favorite and recently virtually-departed friend. So maybe, in a way, it's better he's no longer here to see what we've become.
My only real criticism is that, since Spell Critical is the only privilege of the Eldritch Knight, one should try to get to it as soon as possible to fully experience the class. This usually means going Wizard 5/EK 10 or Fighter 1/Wizard 5/EK 10. Getting to the last EK level at character level 19 means that you will play with what makes your class unique only for the last two levels of your playthrough, which usually don't last very long (but maybe I'm wrong here, I haven't reached that point yet).
I don't know how retraining works with mythic levels and prestige class' requirements, but maybe it's possible to use your merged spellbook to satisfy EK's requirement with a weird build like Fighter 2/Sorcerer 4, thanks to your increased CL. You would still get a gimped CL compared to a full caster, but at least you'll get to EK 10 by level 16 (just like a pure Sorcerer would).