I beg to differ.
First of all, passives are affected by your ap and ad no matter how you have obtained it, be it by runes, masteries or items. And also, passives are not triggered, they are always up while actives are triggered.
Second, you are talking about giving 20 AP away for +12% spellvamp which is not that much to be honest (pretty much the same price). I am not saying your way is not good but it's really the choice of the player since there is not only one way to play a champion on AP Carry. I never had troubles using this build unlike other builds.

I will post a photo of my results during a normal PvP match using this build, specifically in this order.

the runes ur using arent triggering both passives at lvl 1

Rylais is also rather expensive for first item.

Better (in my opinion) to build hextech revolver and then giant belt your way to rylais.

Reason being that hextech gives you both sustain and dmg for less gold, which is perfect for first item.

Anyhow these are only my thoughts

I will do all of these things you have mentioned, pretty soon. I just need to find the time for it. I will keep on updating this.
Thank you for your advice on the video as well :) (that is something I haven't thought of)

You could write about item choises, summoners spells, runes, abd out some visualisation .
It would be great!
Anyway build is very good :D