First of all, for thoose who don’t know what is Cel Shading, a.k.a. Toon Shading, it is the technique used in some games, like The Legend of Zelda: Breath of the Wild, to give the game atmosphere more of a toon looking. Here are some examples:
It may look good in Unturned if done right, without outlines, but with some stylized fresnel and ramp lightining (something close to what the Breath of the Wild looks like). It usually looks good on almost every low poly game.
For test purposes, maybe it could be included in some demo version, so the community could determine if it looks good or not.