Besides the built-in emoji font from Apple, Microsoft or Google, you can also display emoji's with the open source Twemoji or OpenMoji fonts, or the commercial JoyPixels font.
Twemoji is used by this very forum
For ease of entering emoji's, you could put an emoji picker under the "Insert" tab next to the special characters button.
Touch Bar support would be nice too for people who have a MacBook Pro.
But that's not essential, as you can also just copy and paste emoji's into your document. I consider being able to display emoji's properly essential however.
An emoji like