Should they replace (or remove) the AP scaling of non-hybrids?
There are a quite few champions who, for a while now since Trinity Force hasn't had AP since preseason 5, make no sense to have AP scalings. Especially those who can't effectively use Guinsoo's Rageblade. Or even just tanks who aren't effective building it in the first place.
That would be:

There may be more, but these are the ones that stood out to me who have no possible effective build for AP outside of featured game modes, assuming they're against evenly matched enemy players.
I think they should either have the AP scaling replaced with a lesser AD scaling, or simply have it removed and replaced with higher bases at later levels. But to have a stat the champion can't effectively build doesn't make sense when the the other 90% of champions aren't gimped in that way.
The thematic defense doesn't work, because there are so many examples of the abilities that seem magic scaling AD and vice-versa. Riven's Ultimate, Ali's, Akali's, and Kat's entire kits, etc.
The "having no scaling looks weird" defense doesn't hold up, either, because having the wrong scaling for the kit looks a hell of a lot weirder.
And considering that many of these champions are underperforming, the claim that there's no power budget alotted to their AP scaling is missing its premise. To be able to say no power is budgeted into an extremely high AP scaling, you'd first have to have a champion who, without being able to buy any AP, is still performing at 50% or above.