I think you should have included more characters... IMO
can't, poll allows a max of ten. I had to eliminate some who do have some demand too, even if it's much lower than those listed in the poll. most notable from these are:
Ashrah - potential there, too low demand
Hotaru - I don't see why, but some do see potential in him, also low demand
Bo Rai Cho - excluded because five year olds won't play the game for the vomit stuff, despite so many saying his story role is important. he can stay there forever and never playable again hopefully
Li Mei - a bit of demand, probably too low overall though, perhaps too vanilla and hence sareena is in the list instead
Noob Saibot - due to cage's stunt double
Sindel - probably wouldn't sell well / low demand
skarlet - possibly the girl that attracts the most from the ones left available, kind of shut down by NRS in tweets
frost - weird higher demand, but gently shut down by NRS in various tweets
sektor - classic favourite, only left out because I had ten slots and more people seem to want Cyrax instead