I guess Finn does make sense since Stranger Things also films in Atlanta but I feel like he is such a big name that probably would have been rumored.
Billy and/or Teddy probably will be played by big-name actors regardless considering they already cast an unheard actor for Eli.
I just hope we don't end up with the same issue Runaways had by casting Gregg Sulkinn as Chase and completely missing the mark on the character.