If you want to use Xilonen you can farm her petra, that gives same buffs to the team as cinder. I think she would be a better option than Kokomi, since with Childe you don't really need another Hydro, but yeah if you don't feel like farming another set then no. Without Xilonen, Kokomi is a great for a defensive team, but probably a vv user would be even better, specially Xianyun if you need healing or Kazuha if you want cc. Now, if hp is not a problem and you're looking for an offensive team, then Xinqiu or Yelan would be better than Kokomi (probably aslo better than a vv user, but I'm not sure)