There is one from 2021 already: Extended set of Emojis in jolla keyboard - #14 by Apostle
I have been thinking the same what would be best place for emojis in SailfishOS. At least in android there is button on top of the keyboard where you get to the emoji selection view. I don’t mind that much of how SFOS currently does it, but the emoji selection is just suuuper small. My suggestion would be that there would be category button in below of emoji keyboard and then you could scroll down that category to see all emoji options. There is patches for emojis, but I try to keep my system patch free. Closer to the vanilla better as I have zero knowledge to tackle any possible problems…