Though it sucks the Pixel Remasters don't have the extra content, but since these games are on PC that I think it is doable to recreate the missing content for FF1, and FF2.
FF3 maybe that one will be down to taste since its new content was on the 3D version.
FF4 might prove to be the most time consuming to recreate the missing content because they added quite a bit of it in the GBA version when it was introduced.
FF5 same situation with FF4.
FF6 should be simple to recreate though its not a huge loss since the content in that one wasn't the greatest, also the sprites for the characters can easily be replaced with the original SNES versions which can easily be done without much effort if you know what you're doing with the sprite sheets.
Ultimately if they do console versions of these games that unfortunately it won't be the superior versions due to the power of PC modding.
I think we're all lucky these games are not console exclusive, its a win-win.
Just you all watch, there is probably going to be some professional modders that will probably create some anniversary modpacks at some point.
I still think FF4 PSP will still be regarded as the best version, but I can understand that the Pixel Remasters are supposed to be celebrating the original versions.
I can also see why they did this because they want new fans to experience what we experienced in the past (though its not completely 1:1).