LegitKorea was really on to something when he tried this on one of his streams. Pekkin is also a complete and utter genius (psycho) when he did this build in one of his vids.
As an avid ahri support enjoyer though, may I ask why you think spellbook is better over glacial or running electrocute in domination? I find the most important part of winning ahri support games is the laning phase, and spellbook is pretty much useless early on.
Ahri support is really good when you are ahead as you can assist your team with making picks with the ultimate and everfrost combo, especially with glacial augment's follow up slow.
I also like to run cheap shot and ultimate hunter instead of manaflow and transendence, as I find the CDR on ult really helpful for making picks and the cheap shot can be that little bit more damage the more charms you can land in the lane. The transendence CDR isn't as good as ultimate hunter imo, as it is easier to get early on and the CDR applying on ahri's other abilties isn't as important. More charms are nice with the transendence CDR, but not necessary.
I'm all ears for new builds though, I love experimenting with off meta stuff too and am in a similar elo as to you.

Oooh and before I forget, I think yumi should be in the extreme section for counters as ahri really sucks against her due to the speed and sustain she provides. I have versed it a couple times, and it has been horrible each time I've played the matchup (I might just be bad at playing the matchup lul). I think thresh also deserves to be in major as charm DOES NOT cancel hook startup time, and when he gets on top of you, there is not much that can be done pre 6 really.